Prime Minister Gordon Brown "knows nothing" about shadow home secretary David Davis' claims he warned him about an MP being bugged.

A Downing Street spokeswoman said: "We have received a number of letters from David Davis since the beginning of December, on matters such as the Humber bridge, the Security Industry Authority and Licensing laws.

"But having conducted a detailed check, we have no record of receiving a letter about the bugging of MPs. Consequently the Prime Minister knows nothing about this letter."

The statement follows claims Labour whip Sadiq Khan was bugged on two occassions by Scotland Yard's anti-terrorism unit, while he visited a constituent in prison.

Justice Secretary Jack Straw has launched an internal inquiry into the allegations, which suggest a breach of rules aimed at protecting MPs from eavesdropping by police.

The constituent visited by Mr Khan was an old childhood friend, Babar Ahmad, who is in detention awaiting deportation to the USA over the alleged running of a website raising funds for Taliban and Chechen terrorists in the 1990s.

The Sunday Times newspaper claims it has seen a document which showed there was internal concern about bugging the MP but it went ahead anyway.

A spokesman for Scotland Yard said it was "not prepared to discuss" the allegations.

Khalid Mahmood, MP for Birmingham Perry Barr, said: "I certainly would not advocate or support what they have done.

"I don't think for a minute Sadiq Khan would do anything not in the interests of this country. He is a member of this country, of parliament and is a whip and what has happened is highly questionable.

"It's very regrettable. This member of Parliament deserves the respect which he has been given by his constituents.

"If he felt there was an issue of national interest Mr Khan himself would have made police aware. It is the wrong way for police to act."

Jack Straw, Justice Minister, said he had no knowledge of the facts but has ordered an internal inquiry.

He added: "It is completely unacceptable for an interview to be conducted by a MP on a constituent matter or in any other issue to be recorded."

Mr Khan is said to be "outraged" over the bugging allegations adding: "This is an infringement of a citizen's right to have a private meeting with his MP."

The bugging is said to have taken place at Woodhill prison in Milton Keynes in 2005 and 2006.

Mr Khan was meeting Mr Ahmad while campaigning against his extradition.

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