Clowns to the left of me, jokers to the right: Cameron buffeted on all sides

David Cameron faces challenges from his left and right flank today, as Liam Fox offers a right-wing message to Tory activists while Vince Cable threatened to vote with Labour on mansion tax.

The business secretary told the Today programme he may back Labour's motion, just days after he distanced himself from Downing Street by suggesting the government needed to borrow more.

"If it is a real commitment [to a mansion tax] I would certainly welcome that," he said.

"Nick Clegg and I are very strong supporters of a mansion tax but we will have a look at what the opposition motion says."

Cable insisted his plans for a boost to infrastructure spending would require only minor servicing of the UK's debt because of the historic low levels of interest rates it enjoyed.

The business secretary continues to insist he is only calling for a "Plan A+" rather than a 'Plan B', but by even countenancing the prospect of borrowing more Cable is flatly contradicting David Cameron's insistence that "there is no alternative".

The only point of agreement between Cable and Fox is their joint view that the ringfencing of budgets is unhelpful.

Currently the NHS, the aid budget and schools are protected from spending cuts. Cable said the approach was "unbalanced".

He added: "As a long-term approach it isn't very sensible."

Fox's speech to the Institute of Economic Affairs, titled 'The Right Approach for Britain's Economy', opposed ringfenced budgets,  demanded a cut to all public spending for five years and called for for a reduction in capital gains tax to zero per cent.

"This would create a tax window where businesses that are sitting on assets might be encouraged to sell, investment in capital becomes more attractive and where hundreds of thousands of second homes might come on to the market," he said.

The "great socialist coup of the last decade was making wealth an embarrassment – it is not," he added.

Fox has diligently cultivated local associations since he was forced to step down as defence secretary.

He enjoys a very good reputation among backbenchers but any future leadership bid is more likely to come from Theresa May, whose speech to the ConservativeHome rally at the weekend went far beyond her Home Office brief.

The home secretary suggested the Tories should run in 2015 on a promise to leave the European court of human rights and raised rumours about Michael Gove's role as a possible running mate.

Cameron has been suffering increasingly vocal outbursts from his Cabinet ministers and backbenchers since the Tories came third in the Eastleigh by-election.

That disastrous performance saw many Tories give up all hope of winning in 2015. A Lord Ashcroft poll of marginal constituencies cemented that impression, with figures showing Labour is on course for a majority of 84.

Despite the anarchic appearance, Downing Street may secretly be a little pleased with the breadth of opposition to Cameron.

With voices on left and right demanding a change of direction, it is easier for Cameron to portray himself as the responsible centrist staying the course on deficit reduction.