The Conservatives are to seek "urgent clarification" on the rules governing questions to the Prime Minister after David Cameron was blocked by the Speaker of the House of Commons from asking Tony Blair about his likely successor.

Opposition whips have decided not to mount a formal challenge to Michael Martin’s ruling, which caused uproar at Prime Minister’s Questions in the Commons today.

But a senior aide to Mr Cameron said that the party was concerned that the ruling could stop him from asking questions which go to the heart of how Britain is governed.

There were furious scenes in the chamber Mr Martin blocked the Conservative leader from repeating a question he had already asked three weeks ago as to whether Mr Blair stood by a remark in January that he was "absolutely happy that Gordon will be my successor".

Mr Martin got up from the Speaker's chair to interrupt even before Mr Cameron had finished the question and, to Tory jeers of disbelief, told him that PMQs should only be used to ask Mr Blair about "the business of the Government".

As the angry protests of Tory backbenchers threatened to drown out his words, Mr Martin, who was elected as a Labour MP but has to remain neutral as Speaker, even threatened to suspend the sitting.

Mr Cameron joined in the protests, angrily demanding to Labour jeers: "Are you honestly saying we cannot ask the Prime Minister of the country who ..." before Mr Martin intervened again to say he had no right to ask who Mr Blair was supporting for an office in the Labour Party.

That forced Mr Cameron to change tack. "Perhaps I could just ask who you’d like to see as the next Prime Minister of this country?" he said.

To laughter on all sides - and ignoring the fact that Mr Cameron had never originally mentioned Mr Blair's successor as Labour leader - Mr Martin responded: "I’ll allow that. That’s in order."

Mr Blair then heaped praise on the Chancellor for delivering the lowest inflation, lowest unemployment and lowest interest rates in the country’s history which was - referring to Mr Cameron's own career history - "a rather better recommendation than having spent some time advising Norman Lamont on Black Wednesday".

The senior Cameron aide described the ruling as "bizarre and extraordinary" and said that Opposition whips had considered challenging it.

He said: "We are not going to make a formal challenge. But we will be seeking urgent clarification from the Speaker as to the types of questions we can ask. We feel that questions about relationships inside Government and inside the Cabinet go the heart of how this country is governed."

Since Mr Cameron became Tory leader, the Conservatives have adopted a strategy of targeting their strongest fire at the Chancellor, in a bid to exploit apparent differences between 10 and 11 Downing Street and chip away at the reputation of the man they expect to lead Labour into the next election.

They have also used every opportunity - including Mr Blair's weekly question and answer sessions - to suggest to voters that Mr Blair does not trust Mr Brown to carry on his programme as prime minister and does not want him to be his successor.

Mr Martin is Labour MP for Glasgow North East, but his role as Speaker requires him to be politically neutral in presiding over debates in the House of Commons.

In recent weeks, he has also rebuked Mr Blair for trying to use PMQs as a platform to criticise Conservative policies.

Mr Martin’s election in 2000, following the retirement of the much-admired Betty Boothroyd, broke with convention as it meant that two Labour MPs in succession had occupied the post, which is normally held by the two major parties in turn.

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