The government's decision to delay a 3p-per-litre increase in fuel duty from August to January is part of an "overall broader plan of helping with the cost of living and business growth", Treasury Minister Chloe Smith has said.
As MPs debated the Finance (No 4) Bill, which brings into force the tax measures which were announced at last month's Budget and the March 2011 Budget, on 2 July 2012, Ms Smith claimed the plans would leave the deficit-reduction strategy intact.
The £550m cost of the policy shift would be met through "greater than expected savings" in departmental budgets, she told MPs.
But Labour's Cathy Jamieson cast doubt on this claim.
As MPs moved on to debate the government's changes to income tax policy, Ms Jamieson repeated Labour calls for the government to scrap its reduction in the top rate of income tax from 50% to 45%.
She said: "When times are tough and there is less money around we have to make absolutely sure the burden of deficit reduction is fairly shared."
Provisions in the bill will increase the threshold at which the bottom rate of income tax is payable from April 2012.
Corporation tax will be cut to 23% from April 2013.