Opposition Leader Tony Abbott will oppose Kevin Rudd's plans to tighten the rules on tax benefits for salary-sacrificed cars, even though it means rejecting a $1.8 billion boost to the budget.

After labeling Labor's  announcement as ''policy on the run'', Mr Abbott and shadow treasurer Joe Hockey confirmed on Friday that they would oppose Labor's controversial crackdown on the fringe benefits tax.

''I just deeply lament the fact that we have a government that doesn't get that announcements have consequences,'' Mr Abbott said.

''If you suddenly change the rules in which an industry is operating you can convulse it in ways that can destroy jobs.''

Asked what message he had to the fleet sales workers who had lost their jobs after Labor's policy change this week, the Mr Abbott said: ''I bleed for them.''

The Coalition's announcement comes after Industry Ministry Kim Carr flagged that the Rudd government could change its car plan to compensate Australian manufacturers if its reform of the fringe benefits tax leads to ''unintended consequences''.

As Treasurer Chris Bowen stood firm, and as car leasing companies said they would start laying off staff on Friday, Senator Carr met car manufacturers and finance companies to hear their fears about the tax change.

Leasing firms say the tax could wipe out the novated lease business, which now sees a third of new cars sold to employees who get a tax break for buying through salary sacrifice.

Novated lease company nlc announced 74 redundancies from its 143-strong workforce on Thursday.

Holden and Toyota fear the change will cause a significant impact on their battered sales. Traditionally, government and business users bought three-quarters of all new Holdens and Falcons, although most business purchases are now imports.

The car industry is considering an advertising campaign to protest against the changes, according to reports on Sky News on Friday.

Senator Carr said he was listening to the industry's concerns, and the government would ''go about implementing this policy change in a sensible and considered way''.

But he said the tax change was justified, and had gone through the cabinet process. If the industry suffered ''unintended consequences'', he said, the government would consider that in the context of carmakers' calls for changes to the New Car Plan.

Treasury estimates the tax break costs revenue of $800 million a year, which is almost twice the cost of the car plan. But the car plan is set to taper off, and Holden is pushing Labor and the Coalition to offer increased support to keep it manufacturing after 2016.

''I have had numerous discussions with the automotive manufacturing industry about our proposals and will continue talking with them,'' Senator Carr said.

''The purpose is to give companies the opportunity to talk through with us their view regarding the impact of these changes. Clearly, we have our own view of this, but we want to hear industry's views.''

A war of statistics heated up between government and industry over the change. Leasing firms said most of their clients earned less than $100,000 a year, while Mr Bowen said two-thirds earned more than $100,000.

''Treasury analysis indicates the changes affect around one in six employees earning over $150,000 a year, compared to around one in 25 employees earning between $60,000 and $100,000 a year,'' Mr Bowen said.

He likened the outcry to the 1985 campaign by restaurateurs against the introduction of the fringe benefits tax, which they claimed would shut down their business. In fact, the tax barely registered on the industry's rapid growth.

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