Labour's election co-ordinator Ed Miliband has said that if re-elected they will not make any "big spending commitments".
He told Sky News that as there is "less money around" there will be tight controls on costing and spending.
Labour are set to publish their manifesto tomorrow.
The Conservatives are expected to launch their manifesto on Tuesday.
Party leader David Cameron told the Sunday Telegraph that if elected he will govern for "everyone in Britain".
He said that many of Margaret Thatcher's policies divided the country and he would try a new approach.
"Should we try today, in 2010 and into the future, in doing difficult things like cutting the deficit – should we try and take the whole country with us? Yes."
The paper also publishes an extract from his foreword to the Conservative manifesto:
"There is no law that says we must accept decline. We have the energy, the ideas, the ambition to get Britain back on track. And that includes everyone in Britain, wherever they live and whatever their circumstances."
The Lib Dems are also set to unveil their manifesto this week.
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The party's manifesto group chairman Danny Alexander said there had been 13 years of Labour failure and all Gordon Brown has to offer is "business as usual".
"People want change and they want fairness," he said.
"And they will never get that from Gordon Brown.
"Only the Liberal Democrats will make the tax system fairer and clean up politics."
Today's Sunday Times/You Gov poll puts the Conservatives up one to 40 per cent, Labour up three to 32 per cent and the Lib Dems down two to 18 per cent.
A News of the World poll of 96 Labour-held key marginals that the Conservatives must win puts Labour on 37 per cent, Tories on 36 per cent and Lib Dems on 19 per cent.
A Comres/Independent on Sunday/Sunday Mirror poll has the Tories on 39 per cent, up two, Labour up two on 39 per cent and Lib Dems on 16 per cent, down four.
The Sunday Telegraph/ICM poll "sees the Tories' lead over Labour rising from four points on Tuesday to eight today, with Mr Cameron’s party on 38 per cent, Labour on 30 per cent and the Liberal Democrats on 21 per cent".
And the prime minister's wife Sarah is writing an election diary for the Sunday Mirror.
Today she reflected that she has had "an interesting start to life on the road".
She said her motto for this campaign "is not about big P politics, as in people shouting at each other in the House of Commons. It’s about the policies that make life better or worse for people in their everyday lives".
