Ed Balls will today intensify the attack on what he will brand the Tories' £25bn of "desperate" unfunded promises, claiming they will cost every British household more than £1400 a year.

The Shadow Chancellor's campaign speech comes after deputy Labour leader Harriet Harman launched her party's women's manifesto to woo female voters but also after Ed Miliband failed to confirm that, if Labour won on May 7, she would become Deputy Prime Minister.

On the stump in the Midlands, Mr Balls will challenge David Cameron and George Osborne to come clean and explain where the money is coming from for the pledges they have made.

He will also call on all the main parties to back legislation, which would require the Office for Budget Responsibility, the UK Government's independent forecaster, to audit manifesto spending and tax commitments in all future elections.

The Labour frontbencher will point to how the Tory leadership's line on more pledges - that people should trust it because of its track record - was simply not credible given that while the Coalition had given a huge tax cut to millionaires, it had piled misery on ordinary working people by raising VAT and cutting tax credits; costing ordinary families on average £1100 a year.

"Everyone knows it will be working families, who end up paying the price again if the Tories win the election. The Tories have now racked up £25bn a year of promises, which they refuse to explain how they will pay for," Mr Balls will say.

"£25bn," he will add, "is the equivalent of £1439 a year for every working household in Britain. That's the price working families will pay under the Tories for panicky promises made in the middle of a desperate campaign."

In London, Ms Harman launched her party's women's manifesto, A Better Future For Women, saying: "For so long until quite recently, politics was just a bit of a men-only game; so we need to highlight the fact that politicians are there for women and democracy is there for women as well as men."

She also floated an "incredibly important" plan to allow grandparents to take unpaid to leave to look after grandchildren and help out pressured parents.

But earlier, Mr Miliband conspicuously refused to say whether his colleague would become DPM if Labour won power when asked about it on BBC Radio 4's Woman's Hour.

He said: "Harriet is an incredibly strong...asset to our party; I can't say fairer than that. But I'm not going to start anticipating what might happen after the election."

Yet at the weekend, Ms Harman made clear her intention to become DPM, saying: "Well, I'm Shadow Deputy Prime Minister and I hope that we'll get into government."

Last year in a speech, she criticised ex-PM Gordon Brown for not making her DPM when she was elected Labour's deputy leader.

"Imagine my surprise," she said at the time, "when having won a hard-fought election to succeed John Prescott as deputy leader of the Labour Party, I discovered I was not to succeed him as Deputy Prime Minister. If one of the men had won the deputy leadership, would that have happened? Would they have put up with it? I doubt it," Ms Harman added.