Parents and grandparents will be allowed to draw on their pension pots to secure deposits for young family members in a bid to boost home ownership, Nick Clegg said.

The Deputy Prime Minister said detailed proposals were being drawn up by Liberal Democrat ministers as part of efforts to make the economy "fairer".

But he also declined to commit to pushing for any specific wealth tax despite promising activists at the party conference that he would play hardball with the Tories on the issue.

Speaking on BBC1's Andrew Marr Show from the Brighton gathering, he said: "This is part and parcel of something which I think most people agree with which is that as we fill in the black hole in the public finances we have to also got to make sure that we do not put Humpty Dumpty back together again and make the same mistakes, that we re-wire the British economy and make it fairer and give people more opportunities.

"Let me give you one very good example: we have thousands of young people who are desperate to get their feet on the first rung of the property ladder but deposits have doubled and the number of young people asking help from family members has doubled.

"So I can announce today that the Government is going to do something that hasn't happened before: we are going to work out ways in which parents and grandparents who want to help their children and grandchildren buy a property of their own, we are going to allow those parents and grandparents to act as a guarantee if you like so their youngsters...can take out a deposit and buy a home.

"It is a pension from property scheme."

Mr Clegg sought to rally his party last night by promising to claw back more money from people who "sit on a fortune" amid rumblings about his leadership and consistently dire opinion poll ratings.

Aides said he would insist on fresh taxes for the wealthy as the price for accepting billions of pounds of extra spending cuts when the coalition sets budgets for 2015-16.

As part of that agenda, Treasury Chief Secretary Danny Alexander revealed today that a crackdown on tax dodgers was being extended to all those worth £1 million or more.

But Mr Clegg appeared to signal today that he did not expect the promised fairness to come in the form of a specific extra levy such as the mansion tax on £2 billion-plus properties favoured by the party.

Asked if he believed he could persuade his Tory coalition partners to accept a form of wealth tax, he said: "I think there is a very considerable chance, because we have already done a lot of it, to make sure that the top pay more tax.

Pressed to provide a single example of a new measure that could be introduced.during this parliament, he conceded that "so far I have failed" to persuade David Cameron and George Osborne to accept a mansion tax.

"But the mansion tax is not the only way in which you can make people at the top make a fair contribution to this huge national effort of balancing the books.

"We have already illustrated through capital gains tax, through stamp duty, through tax avoidance and many other measures ... the top 10% pay more and we can do more of that.

"There are numerous ways that we have already done it and numerous ways that you can do more of it. It will bore viewers if we go through all the great encyclopaedic... "

Pushed again, he added: "All of the kind of things we have already done, whether it is on capital gains, whether it is on high property transactions, all of that you can do more of."

Mr Clegg has already signalled that he would veto any bid by the Treasury to slash another £10 billion from the welfare bill and insist on the pain of future austerity measures being placed more on the better-off.

"I will not accept a new wave of fiscal retrenchment, of belt tightening, without asking people at the top to make an additional contribution.

"I don't think you can ask people on middle and low incomes, who after all are the vast majority of the British population, to bear the brunt of this adjustment."

The Deputy Prime Minister insisted his party would "not be bound hand and foot" to Tory spending plans beyond the 2015/16 year as it seeks to differentiate itself ahead of the 2015 election.

But it had no choice but top adopt joint spending plans that went some way beyond the poll as the present parliament would extend into the 2015/16 financial year.

Mr Alexander said that an expanded unit of tax inspectors would "sniff out" cheats.

The move will mean 200,000 more people will be targeted by HM Revenue and Customs' affluence unit, set up originally to study the affairs of the 300,000 with assets and property of more than £2.5 million.

There will also be separate moves to stop high-earning BBC personalities from using tax avoidance schemes and fines for tax-dodging footballers.