SIR IAN BLAIR, the scandal-prone head of Scotland Yard, was ordered last night to explain why he secretly recorded a confidential telephone call with a Cabinet minister, The Times has learnt.

The conversation with Lord Goldsmith, QC, the Attorney-General, was taped last September and the Home Secretary is demanding that Sir Ian justify himself.

In a bizarre twist, The Times has been told that the call was about the admissibility of telephone tap evidence in British courts.

Sir Ian could now face an investigation for breaching data protection laws by failing to tell the Attorney-General, and at least five other callers, that he was putting them on tape. Charles Clarke also wants Sir Ian to disclose if his tape collection includes private discussions with other senior ministers.

Lord Goldsmith knew nothing of the recording until Scotland Yard and the Home Office alerted him at the weekend.

The Attorney-General was said to be “extremely angry” and complained to Mr Clarke that there had been a grave breach of protocol.

A spokesman for the Attorney-General said: “All I can say is that we have been informed by the Metropolitan Police that a conversation between Sir Ian Blair and the Attorney-General had been recorded and that it was recorded without his knowledge or permission.”

It is thought to be unprecedented for a conversation with the Government’s senior law officer to be recorded, let alone by the country’s most senior policeman.

The Metropolitan Police Authority which has the power to discipline Sir Ian, will meet today to consider what action it should take. Yesterday one senior member said that the Commissioner’s action “destroys the basis of trust”.

Met sources said that in all six telephone conversations were recorded, including the call with Lord Goldsmith, but critics are certain to query whether there were more.

Scotland Yard yesterday admitted that there were three secret recordings of calls to the Independent Police Complaints Commission (IPCC); one with Nick Hardwick, its head; one with his deputy John Wadham and the other to the then director of investigations Roy Clarke, who is a former top detective at the Yard. These calls took place on July 22, in the hours after the shooting of Jean Charles de Menezes, the Brazilian electrician shot by police in a botched attempt to prevent a suicide bomb attack. Sir Ian and Mr Hardwick were embroiled in a row over whether there should be an independent examination of Mr de Menezes’s death.

The digital recordings were discovered when the IPCC began investigations. Transcripts of the damaging material have been handed to the commission. Peter Goode, its director of operations, is investigating why they were taken.

The people taking part in the other two conversations have not been identified but the discussions were said by police sources to be unimportant.

It is standard practice for civil servants and officials to listen in to conversations involving government ministers so that they can make a written note, but it is regarded as unacceptable for anyone to make a recording without the minister’s knowledge or permission.

The row could not come at a worse time for Sir Ian. Officers from his force could face prosecution over the shooting of Mr de Menezes at Stockwell station in South London last July.

Sir Ian is already under investigation over his comments — and the information put out by the Yard — in the hours following the shooting.

Richard Barnes, the deputy chairman of the Metropolitan Police Authority, said that he was “horrified” and added that the secret taping “smacks of Nixon”, a reference to Richard Nixon, the disgraced US President.

“This says no one can have a private conversation with him and that would worry me enormously,” Mr Barnes said.

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