NICK Clegg launched the Liberal Democrats election manifesto with an attack on Alex Salmond as his policy chief signalled they would block the Tories planned £12bn welfare cuts.

Education Minister David Laws, now in charge of party policy, indicated that the slash in the benefits budget would be a dealbreaker in any coalition talks after May 7.

Earlier the Deputy Prime Minister claimed voters could choose who held the balance of power in a hung parliament -the LibDems or parties of "grievance" such as the SNP or Ukip.

Every Liberal Democrat MP would be a bar between former First Minister Mr Salmond and the door to No 10, he added.

He defended his focus on Mr Salmond instead of current SNP leader Nicola Sturgeon saying only one of them was standing in the General Election.

And he appealed directly to voters at yesterday's manifesto launch in London: "If you want to stop Salmond the answer is very simple, vote for the fantastic (Lib Dem) Christine Jardine in Gordon."

He also asked voters to consider what would "become of Britain" if Mr Salmond or Ukip's Nigel Farage got into into government.

"I'm not denying that either David Cameron or Ed Miliband will be Prime Minister," he said.

"What really matters is who they will have by their side...

"Do you want Nigel Farage walking through the door of No 10? Do you want Alex Salmond sat at the cabinet table? Or do you want the Liberal Democrats?

He also set up the tone for future conflict in any Labour-Lib Dem coalition by saying his party would put the "brains" into any Ed Miliband-led government's economic policies.

Aides later refused to be drawn on whether or not Mr Clegg considered Labour's shadow chancellor Ed Balls "brainless".

Ms Sturgeon hit back saying that the Lib Dems "cannot be trusted" after their 2010 U-turn on university tuition fees.

Mr Osborne also hit out at the party saying a vote for the LibDems or Ukip would pave the way for a Labour government, which he predicted would result in "chaos, job losses and cuts to family incomes".

In the manifesto the LibDems also pledged to scrap the so-called 'bedroom tax,' despite being part of the government that introduced it in the first place.

The party has also toughened its position on Mr Osborne's planned cuts to welfare.

The Tories have refused to set out where the reductions in spending will come from.

Mr Laws said agreeing to that plan would be "impossible".

In the strongest comments yet on the issue he said: "It is impossible to see how we would want to sign up to that. We have identified some welfare savings but we are not prepared to go down the Tory route."

He added: "To find savings of the scale that the Tories are suggesting you would have to do things like make massive absolute cuts to the level of disability benefits, you'd probably have to means test child benefit way down the income distribution, you'd have to make

huge cuts to the benefits for young people including those in employment."

However, he was less unequivocal about the Tories planned EU referendum and also refused to rule out the possibility of the Lib Dems doing a deal with Northern Ireland's DUP as part of a 'rainbow coalition' in the event of a hung parliament.

Mr Clegg said his party's manifesto was an "an insurance policy against a government lurching off to the extremes".

The front page of the Lib Dem manifesto sets out the party's five priority policies that it says it will fight for in any coalition talks.

They include balancing the national budget in a fair way, guaranteed education funding "from cradle to college"; an increase to £12,500 in the income tax personal allowance, an £8 billion hike in NHS funding; and five green laws to protect the environment.

Mr Clegg made a plea for voters top help the party prevent the SNP or Ukip holding the balance of power.

He said "The truth is a few hundred votes in a small number of seats could decide whether it is Liberal Democrat MPs, Ukip MPs or SNP MPs who the next prime minister will be forced to listen to. There is a very thin line between Britain being governed by a coalition with a conscience or a government with a grievance."

SNP Deputy leader Stewart Hosie said: "Having effectively ripped up their 2010 manifesto when they entered coalition with the Tories, people no longer believe a word the Lib Dems say."