As five Scotland Yard detectives boarded a flight to Pakistan last night Britain was accused of providing a fig leaf for President Musharraf by helping the investigation into Benazir Bhutto’s assassination.

Mr Musharraf angrily denied allegations that he or his Government was behind Ms Bhutto’s death and said that the British detectives, due to arrive this morning, would be able to examine fresh evidence.

The Pakistan People’s Party, which Ms Bhutto led until her death, repeated its call for a UN inquiry and accused Mr Musharraf of using Britain to legitimise a flawed investigation. “It is too little too late. By half-heartedly declaring this international involvement, he is attempting to cover up the cover-up,” Farhatullah Babar, a spokesman for the PPP, told The Times. “He needs a fig leaf of international assistance to cover up the evidence about the real killers.”

The accusation gave a foretaste of the charged political climate that the British detectives will find when they arrive in Islamabad, the capital, to join one of the most sensitive investigations in Pakistan’s 60-year history.

The Government has blamed Ms Bhutto’s assassination on Baitullah Mehsud, a top leader of the Pakistani Taleban whom it says has close links to al-Qaeda. He has denied any involvement and many Bhutto family members, PPP leaders and ordinary Pakistanis believe that the Inter-Services Intelligence (ISI) agency was behind the assassination.

The Government’s case has also been undermined by its decision to hose down the crime scene after the attack, destroying crucial evidence, and its initial claim that Ms Bhutto was not shot, which has been debunked by amateur video footage.

The British detectives, who are from the Metropolitan Police’s Counter-Terrorism Command but have not been identified, will be hampered further by the lack of a postmortem examination on Ms Bhutto, who was buried last Friday in a family mausoleum.

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