The Scotland Yard team charged with investigating the death of Benazir Bhutto have concluded that she died from a head injury following a lone suicide bomber’s blast and not from gunshot wounds, re-affirming the initial findings of the Pakistan government (write Zahid Hussain in Islamabad and Will Pavia).

The British team's findings were swiftly rejected today by the Pakistan People’s Party, the opposition grouping that Ms Bhutto had led. Sherry Rehman, a spokeswoman for the PPP, said: “The party is still looking at the Scotland Yard report, however, it is difficult to agree with its findings on the cause of death.” She added: “We do believe that she was killed by an assassin’s bullet.”

A spokesman for Ms Bhutto’s son, Bilawal Bhutto Zardari, who was appointed party leader after her death, said the report "achieved nothing" and would be used as a “diversion” away from the real issue of finding the killers.

The report on the assassination rules out the possibility that the head injury that killed her was a gunshot wound.

The opposition leader had been standing up in the escape hatch of an armoured vehicle, designed to withstand bullets and bomb blasts, waving to supporters at a rally in Rawalpindi on December 27 last year, when the suicide bomber struck.

As she ducked back into the vehicle, the investigators say she failed to get her head fully below the escape hatch: the blast propelled her into the lip of the hatch causing a fatal head injury.

Dr Nathaniel Cary, the Home Office pathologist consulted by the investigators, is quoted in the report, saying: “The only tenable cause of her rapidly fatal head injury in this case is that it occurred as the result of impact due to the effect of the bomb blast.”

The team, from the Metropolitan Police Counter Terrorism Command, spent three weeks in Pakistan. Last week the team returned to London to carry out forensic tests, before delivering its report to interim interior minister Hamid Nawaz and a nation wracked by political tensions.

Brought in to help settle the controversy over the causes of the death of Ms Bhutto, their findings seem more likely to add fuel to the fire, heightening the tensions in the run-up to parliamentary elections due to be held on February 18.

Wajid Hasan, the spokesman for Bilawal Bhutto Zadari, who is currently a student at Oxford University, said “We don’t accept the report because it tries to cover up the government’s inefficiency in providing security and protecting Ms Bhutto.”

“We want an international inquiry by the UN to look into not only the cause of death but also who was responsible.”

The PPP claims the report was compromised by the fact that officers were working under the Pakistani police, and were limited to investigating the cause of death and not the network behind the attack.

No autopsy was carried out on Ms Bhutto, at the request of her family: her husband, Asif Ali Zardari, said at the time that it was unnecessary as it was clear that she had been shot. Instead investigators had to rely on X-rays taken of her head, and interviews with family members and medical staff who treated her at Rawalpindi General Hospital.

Television pictures that emerged after Ms Bhutto's death appeared to show a gunman aiming a weapon at her as she stood up through the escape hatch, leading to speculation that the assassination was a coordinated attack by gunmen and a suicide bomber.

The British report says shots were fired by a gunman who subsequently detonated an improvised explosive device between one and two metres behind the vehicle.

There is further controversy over the Pakistani investigation into who was behind the attack. The government blamed Baitullah Mehsud, a pro al Qaeda tribal militant leader who is spearheading fighting against Pakistani forces in the lawless tribal South Waziristan region.

In an autobiography to be published posthumously, Ms Bhutto wrote that she had warnings that she was a target of four suicide squads - one sent by Mehsud and another by a son of Osama bin Laden. However, she also accused a cabal of top intelligence and government officials of plotting to kill her, notably in an attack when she returned from exile in Karachi on October 18 that left 139 people dead.

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