The Calabrian Mafia has infiltrated Australian politics at both state and federal levels by ingratiating itself with individual party donors and members of Parliament, according to confidential police reports.

The reports also detail "loopholes" in the political donation system, and say the long-running failure by government to reform it exposes Australian politicians to "potential corruption".

The violent and powerful group known as the Honoured Society, which has extended its networks from Italy and across the world, has gained access to the very highest office bearers in Australia. In one case, a lobbying and donations campaign was aimed at securing a visa for a crime boss later jailed for drug trafficking and implicated in a murder plot.

A year-long Fairfax Media-Four Corners investigation can also reveal that:

• A man who police believe is a senior Mafia boss and alleged hitman met then prime minister John Howard and other top Liberal Party figures at various fundraising events.

The son of another Mafia godfather did work experience at the Australian embassy in Rome while former Liberal minister Amanda Vanstone was ambassador. Previously, authorities were passing through the embassy sensitive information about a Mafia drug-trafficking operation.

In 2013, police circulated a report among state police agencies revealing that the Calabrian Mafia, also known as 'Ndrangheta, had used a number of well-known party donors to put a "legitimate public face" on its push to help obtain an Australian visa for violent crime boss Frank Madafferi.

The report warned that alleged Mafia figures had used various methods to enter "the social and professional world of public officials and through legitimate processes [were able to] achieve influence".

An earlier police report about the visa lobbying said that: "To ensure maximum [political] coverage ... numerous people made approaches to two senators, three federal members of parliament and one state member of parliament ... Donations to the Liberal party were also made by these lobbyists."

Madafferi's visa application was subsequently approved by then immigration minister Amanda Vanstone. Two years later, he was implicated in the world's biggest ecstasy importation and was later charged with murder and convicted for drug trafficking.

One of the Liberal MPs targeted in that campaign, now Small Business Minister Bruce Billson, admitted to the contact with a Mafia-linked donor, but told Fairfax Media the man had "deceived" him.

"The request made of me for assistance … was a contrived veneer covering a far darker and disturbing situation," Mr Billson told Fairfax Media.

Unlike some of his other Liberal colleagues, Mr Billson subsequently cut contact with the donor.

A 2009 AFP report describes "lacks of checks and oversight" in the Australian political donations system as "significant" issues. As it stands, political parties and candidates can "receive significant support and financial contributions through avenues not covered by the statutory disclosure regime", the police report says.

"Loopholes" in the oversight system mean it is "difficult to identify any bribery in the form of political donations".

"The Australian Electoral Commission have attempted to address this on many occasions, however many amendments have not been passed by Federal Parliament," the AFP report said.

The report, obtained under freedom of information laws, was written after an investigation into the Mafia's fundraising activities.

The Calabrian Mafia is one of the world's most powerful crime groups. It differs from the Sicilian Mafia, or Cosa Nostra, which is best known in the United States.

However, both organisations work in similar ways, using threats and violence in both legitimate businesses, such as fruit and vegetables, and illegitimate businesses such as drugs. They both also use money to curry favour with public officials including politicians and police.

The Calabrian Mafia's reach into Australian society was detailed in a highly confidential 2003 National Crime Authority report which also describes the "involvement of Italian Organised Crime figures in … peripheral fundraising activities for political parties".

A search of hundreds of photos from Liberal fundraisers from the early 2000s captures one of the alleged Mafia crime figures and donors named in police files, Tony Madafferi - brother of Frank - meeting John Howard. Melbourne lord mayor and former Victorian state Liberal leader Robert Doyle also appears in photographs with Tony Madafferi.

Tony Madafferi denies any wrongdoing, and has never been charged with an offence, but has been named repeatedly in court proceedings as an alleged organised crime figure with deep ties to Mafia figures and drug traffickers.

He has been named as a violent Mafia figure by witnesses in two coronial inquests, but denied the allegations and was not subject to adverse findings.

Neither Mr Doyle nor Mr Howard knew of Tony Madafferi's links to organised crime.

However, a number of other Liberal and Labor figures, including MPs, have gone further than just meeting Tony Madafferi – they have made representations or lobbied on his behalf, or that of his close associates, after meeting alleged Mafia figures at fundraisers.

Victorian MP Russell Broadbent, who did not respond to repeated attempts to contact him, is among Liberal figures who has attended fundraisers with Tony Madafferi after public warnings about his criminal connections.

Mr Broadbent, Mr Billson and NSW senator Marise Payne attended a 2004 fundraiser organised by Tony Madafferi after meeting political donors linked to him.

A spokesperson for Ms Payne said she "had no knowledge, or any cause to be aware of, any criminal associations" of any figures she dealt with in connection to the Madafferi family's visa lobbying.

Mr Broadbent, Mr Billson and Senator Payne are three among a number of MPs who contacted the immigration minister Amanda Vanstone in 2003 or 2004 as part of a push to get an Australian visa for Frank Madafferi on the basis that his detention and deportation would impact on his family.

In 2000, Frank Madafferi had been ordered to leave Australia by then immigration minister Philip Ruddock on the basis of his serious criminal past and after police warned he would posed a danger to the community.

But in November 2005, after the campaign of donations, lobbying and legal action, Frank Madafferi was granted a visa by Senator Vanstone on what she said were humanitarian grounds not connected to any lobbying or donations. Ms Vanstone did not respond to repeated efforts to contact her.

Less than two years after the visa was granted, Frank Madafferi was implicated in the world's biggest ecstasy importation.

Policing officials who assessed the visa case said in a 2013 report: "There is no suggestion that Vanstone acted corruptly… [but] members of the Italian community, including 'Ndrangheta members and their families and associates, are likely to have ingratiated themselves with her office.

"This case study highlights the insidious ways 'Ndrangheta [mafia] Transnational Australian Group enter the social of professional world of public officials and through legitimate processes achieve influence."

Since 2007, Labor has made several attempts to change the electoral funding disclosure to make it more transparent, but has it has been repeatedly blocked by the Liberal Party.

MARCH OF THE MAFIA IN AUSTRALIA

1922: Three members arrive in Adelaide on the Re D'Italia. They set up cells in Melbourne, Perth and Sydney. Antonio Barbara established the Melbourne cell. The 'Ndrangheta began with rural-based industries, such as fruit and vegetables.

1930: Domenico Italiano arrives in Melbourne and enters into a partnership with Antonia Barbara, making Melbourne the largest Australian cell. Italiano later becomes Godfather.

1928-1940: 10 homicides and 30 bombings attributed to the Society in Queensland as part of sugar cane extortion racket. Mafia also diversifies into drugs and other organised crime.

1962: Melbourne godfather Domenico "The Pope" Italiano and his enforcer, Antonio "The Toad" Barbara, both die of natural causes. Power vacuum sparks a war, called the "Market Wars" for control of Victoria Market.

1963-4: Contestants for control, Vincenzo Angilletta and Vincenzo Muratore, are killed. Victoria Market stallholder Liborio Benvenuto takes over as Godfather in Melbourne.

1977: Anti-drugs campaigner Donald Mackay murdered in Griffith, the centre of Australia's marijuana growing industry. Woodward Royal Commission established.

1981: Griffith drug lord Robert Trimbole identified as a suspect in Donald Mackay's murder. He flees to the United States, then France and Ireland, where a court refused to deport him.

1985: Robert Trimbole dies of natural causes in hospital in Spain

1989: AFP Assistant Commissioner Colin Winchester shot dead in his car in Canberra.

1990: The Australian Bureau of Criminal Intelligence concludes that Winchester was killed because of his operation against a Bungendore mafia drug syndicate.

1990: Market magnate Frank Costa stares down the mafia and takes over the Coles and later Woolworths fruit and vegetable contracts.

1995: David Eastman is sentenced to life for killing Winchester. The conviction is quashed in 2014.

2000: Mafia scion Frank Madafferi has his Australian visa rejected by immigration minister Philip Ruddock.

2005: Immigration minister Amanda Vanstone overturns the decision on Francesco Madafferi.

2007: World's biggest ecstasy bust, with $440 million (4.4 tonnes) of the drug imported in tomato cans from Calabria.

Watch the Four Corners-Fairfax Media exposé on ABC at 8.30 tonight.