The Government's deficit reduction strategy has been defended by Nick Clegg, but he warned that the Tory plan to rule out further tax rises in the next parliament was "nonsense".
Chancellor George Osborne will deliver his set-piece Autumn Statement this week, with ministers braced for official figures expected to show a further deterioration in the public finances after sluggish earnings growth meant tax revenues came in lower than expected.
Deputy Prime Minister Mr Clegg insisted the deficit would be "more or less" halved by the end of the parliament, but condemned the Tory approach to completing the task of balancing the books after the general election through spending plans alone.
Labour has accused the Government of costing the taxpayer tens of billions of pounds in lost revenues through the "abject failure" of its economic policies.
Mr Clegg insisted the deficit was coming down, but accepted progress could be knocked off course by lower-than-expected tax receipts.
"We should be able to see the deficit more or less halved by the end of this parliament," he told BBC Radio 4's Today programme.
"What I accept, of course, is if tax receipts are not as buoyant as predicted, then of course that has an effect. Time will tell whether that is a semi-permanent effect or a temporary blip, but it means that it comes down a little less than originally projected."
He said the coalition had been flexible in its approach to eliminating the deficit, having originally hoped to balance the books by the election.
Mr Clegg said: "I think it is right that this Government hasn't been dogmatic about our deficit reduction plan.
"We have been firm, we have been consistent but when it became obvious ... that the structural deficit was not going to be eliminated by the end of this parliament, far from doing what some people urged me to do - which was to chase our tail, cut even more, implement even more stringent cuts - we said no, we are going to stick to the plan but we will accept that it will take a little longer and it will be three years into the next parliament before you wipe the slate clean and balance the books for future generations.
"I think that combination of pragmatism and consistency is the right approach to something as grave as the black hole in our public finances."
He said the Government was right to continue spending on policies to "renew the economy", with further announcements on housing investment due to be set out by Treasury Chief Secretary Danny Alexander tomorrow.
Mr Clegg acknowledged that further austerity measures would be needed after the election, but rejected suggestions that cuts would have to be even deeper than in this parliament.
"Whoever is in power next year - whether it is Conservative, Liberal Democrat, Labour or any combination of those three - will have to make further substantial savings.
"There is a major difference of opinion between myself and the Conservatives about the role of taxation. The Conservatives, and George Osborne said this yesterday, they will only balance the books on the backs of the working-age poor.
"That is the only part of the population they will ask to make additional sacrifices.
"My party believes you have got to finish the job, but finish the job fairly."
He continued: "We have made about £100 billion of savings during this parliament. We need to make additional savings, whether it's spending reductions or tax increases, in the next three years of the next parliament.
"But the total amount that will need to be done is substantially lower than what we have done during this parliament."
With the Tories committed to £7 billion in tax cuts - raising personal allowances for basic and higher-rate taxpayers - the Institute for Fiscal Studies warned of a new round of austerity after next year's general election, with some Whitehall departments set to lose around a third of their budgets.
But Mr Clegg rejected the Tory approach to cutting the deficit without further tax rises: " My view is what the Conservatives have said is a complete and utter nonsense.
"There is not a single developed economy anywhere in the world that has balanced the books and only done so on the backs of the working-age poor."
Mr Osborne acknowledged that he faces "tough decisions" if he is to balance the books by 2018 as promised and he signalled a fresh squeeze on benefits if the Conservatives regain power in May.
Labour said that ordinary families were paying the price for the Chancellor's failure to fulfil his promise at the last general election in 2010 to clear the deficit and start paying down Britain's debt by the end of the current parliament.
The party said that figures calculated by the independent House of Commons Library showed that over the course of the current parliament, income tax receipts were £66 billion lower than originally forecast and national insurance contributions were down £25.5 billion, while social security spending is £25 billion higher than planned.
It said the loss was the equivalent of almost £4,000 for every taxpayer - resulting in persistently higher borrowing than the Chancellor had forecast.
Labour leader Ed Miliband said millions of families had been left trapped in "the most prolonged cost-of-living crisis for a century".
"For them, this is a joyless and payless recovery," he said.
"The Government's failure to build a recovery that works for everyday people and tackle the cost-of-living crisis isn't just bad for every person affected, it also hampers our ability to pay down the deficit.
"Britain's public finances have been weakened by a Tory-led Government overseeing stagnant wages which keep tax revenues low.
"The result has been David Cameron and George Osborne missing every single target they set themselves on clearing the deficit and balancing the books by the end of this parliament."
Paul Johnson, director of the Institute for Fiscal Studies, said he expected "some bad news" in the Autumn Statement, with the deficit set to remain stubbornly high.
He told BBC Radio 4's World At One: "I think there will be some bad news. I don't think it's going to be bad news on the scale that we got used to in 2011 and 2012 when the economy was doing very much worse than had been expected.
"But, because the shape of the recovery has been very poor in terms of the levels of earnings and productivity growth that we have seen, I expect the independent Office for Budget Responsibility to say that the deficit will be somewhat higher this year than they had expected back in March and, indeed, that it may be somewhat higher going out over the next few years."