Human Rights Watch pointed out that Pakistan has often failed to conduct impartial investigations into cases of human rights abuses.

A team from the Scotland Yard had arrived in Pakistan on January 4, after President Pervez Musharraf [Images] requested British Prime Minister Gordon Brown for assistance in the probe to ascertain the cause of Bhutto's death.

 "Pakistan's investigation into Bhutto's murder lacks independence, transparency and credibility," said Brad Adams, Asia director at Human Rights Watch. "Scotland Yard should never have agreed to only investigate the cause of death, instead of who was responsible. It should not tarnish its reputation by lending its imprimatur to this dubious inquiry."

Though President Pervez Musharraf has accused al Qaeda backed militants of planning Bhutto's assassination, many believe that the government and intelligence agencies were involved in the Pakistan People's Party leader's death.

Initially, the government claimed that Bhutto was killed after she hit her head on the sunroof of her car. But video footage, aired by Pakistani and international media, proved that Bhutto was shot. The confusion over the cause of death had deepened suspicions against the government. .

Human Rights Watch has asked the United States, the United Kingdom, and other concerned governments to urge Pakistan to accept an independent international inquiry, under the aegis of the United Nations, to nab the masterminds behind Bhutto's assassination.

 "Given Pakistan's dismal record at investigations, the need for an independent international inquiry to uncover Bhutto's killers is obvious," said Adams. "Anything less would only increase political tension and instability in Pakistan."