Vince Cable faced a mutiny by his own colleagues yesterday after the party’s new tax policy led to accusations that the Liberal Democrat star performer is high-handed and uncooperative.

In another awkward day for the party, Nick Clegg also faced defiance from frontbenchers on the conference floor with Steve Webb, the pensions spokesman, depicting his electoral strategy as “the audacity of gloom”.

Liberal Democrat MPs, including several frontbenchers, ambushed the party’s Treasury spokesman and deputy leader after it emerged that he had failed to consult them over plans for a mansion tax on properties worth more than £1million.

Frontbenchers had to appear on television unable to answer basic questions, including how properties would be valued, whether the tax would apply in Scotland and whether it would be permanent. Treasury figures suggest that the accompanying policy — to take people earning below £10,000 a year out of income tax — would cost approximately £22billion.

One Liberal Democrat told The Times that Dr Cable’s colleagues were particularly angry because he had been “trying to introduce the policy for years” but had failed to secure the agreement of the front bench.

Even Chris Huhne, the home affairs spokesman, admitted on the BBC that he had not been consulted in advance.

It is the latest in a series of conflicting messages to come from the Liberal Democrats’ conference in Bournemouth, which ends today. First Mr Clegg presented himself as the alternative to Labour before chasing Tory voters with promises of savage cuts. He then recanted this language in an interview with The Times on Monday.

Mr Huhne had planned to accuse William Hague, the Shadow Foreign Secretary, of being a “skinhead who has toured the beer cellars of Central Europe”, but decided against the remark before delivering his speech.

The confrontation with Dr Cable happened at a rowdy meeting of the Lib Dems’ parliamentary party at 9am. Mr Clegg was on a visit to a local farm at the time, which emboldened those present to go on the attack. One of those told The Times: “I don’t think the deputy leader was left in any doubt that he had put a lot of noses out of joint. People do appreciate he’s doing a good job, but people also realise that publishing a pamphlet is rather more premeditated than being put on the spot, and he hadn’t observed the normal courtesies.”

Dr Cable faced awkward questions over whether the tax would apply in Scotland, which he answered unsatisfactorily, according to one source.

Scottish MPs, including Bob Smith and Alistair Carmichael, were among the ringleaders, while Julia Goldsworthy was particularly embarrassed by the mansion tax announcement because she had not been warned about it, even though it was within her local government brief.

The source said: “Eventually he [Dr Cable] showed contrition. He was pretty evasive and in denial when the first complaints came through, but he got the temperature by the end and he said if it hadn’t been recess he could have consulted colleagues.” However, “it could have been bloodier” given the levels of anger.

The criticism represents a particular problem for Mr Clegg because the Liberal Democrats must put all policies to a conference vote. A motion voted through almost unanimously by delegates said that their policy document “neither abandons nor downgrades any existing policy commitments and that the process of prioritising policy commitments will only be carried out in the preparation of the general election manifesto”.

Today Mr Clegg will give his most important speech of the conference season, when he will return to emphasising his party’s progressive message. “Don’t vote Conservative because you think it’s the only option. This is Britain. We don’t settle for second best because we think it’s inevitable. The Liberal Democrats will do things differently in Britain,” he will say.

However, in a line that could dismay his colleagues, he will say: “If you don’t agree with our policies . . . then don’t vote for us.”

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