British police investigating the Lockerbie bombing are to visit Libya, it was disclosed today.

David Cameron announced that officers from the Dumfries and Galloway force had been granted permission to visit the country at a joint press conference in Tripoli with his Libyan counterpart Ali Zeidan.

The Prime Minister said: "I am delighted that the Dumfries and Galloway Police team will be able to visit your country to look into the issues around the Lockerbie bombing."

The officers are expected to travel to Libya in March. It will be the first time police have been allowed to visit as part of the probe.

The move follows months of behind-the-scenes talks. Mr Cameron pointed out that police investigating the murder of Pc Yvonne Fletcher had been able to come to Tripoli three times since the revolution.

That would have been "unthinkable" when Muammar Gaddafi was in power, he added.

On December 21 1988, 270 people were killed when Pan Am flight 103 exploded over Lockerbie.

In 2001, Abdelbaset al-Megrahi was convicted of mass murder and sentenced to life imprisonment.

He was released eight years later on compassionate grounds and he died in May last year.

In December last year the Libyan administration said it was preparing to release all files relating to the bombing.

A formal request was sent to the Libyan government requesting access to the country for police and prosecutors involved in the bombing, in February last year.

A spokesman for Dumfries and Galloway Constabulary said: "It's the first time since the fall of the previous Libyan regime that officers will have the opportunity to make further inquiries in the country."

The bombing of the plane, travelling from London to New York four days before Christmas, killed all 259 people on board.

Eleven residents of the Dumfries and Galloway town also died after it crashed down on homes in Britain's biggest terrorist atrocity.

After protracted international pressure, Megrahi was put on trial under Scots law at Camp Zeist in the Netherlands.

He was found guilty in 2001 of mass murder and was ordered to serve a minimum of 27 years behind bars.

Despite claims that he could not have worked alone, and the lingering suspicion by some that he was innocent, Megrahi was the only man ever convicted over the attack.

He was freed from prison having served nearly eight years of his sentence after he dropped his second appeal against conviction at the Court of Criminal Appeal in Edinburgh. He had been diagnosed with terminal cancer and died in May last year at his home in Tripoli, aged 59.

Scotland Justice Secretary Kenny MacAskill's decision to allow him to return home to Libya to die sparked international condemnation from some relatives of victims and politicians, who had demanded he be returned to jail.

Scotland's top law officer the Lord Advocate, Frank Mulholland QC, and the Chief Constable of Dumfries and Galloway Constabulary, Pat Shearer, met UK families of the Lockerbie victims in London last year after the formal request was sent to Libya to access the country.

The Libyan National Transitional Council had previously confirmed to the UK Government that it would assist the ongoing criminal investigation.

Metropolitan Police officers probing the shooting of WPc Yvonne Fletcher during the Libyan embassy siege in 1984 are due back in Libya over the coming weeks, Downing Street sources said.

The small Lockerbie investigation team from Dumfries and Galloway Police will be making initial contacts with the authorities in the country and discussing how their inquiry could proceed.

Mr Cameron said: "Do I want for all these cases for the truth to be uncovered, for justice to be done? Yes, of course."

A Crown Office spokesman said: "The Lord Advocate welcomes Libyan support for the ongoing investigation. As this is a live investigation it would not be appropriate to comment any further."

Robert Forrester, secretary of the Justice for Megrahi campaign group, which wants an independent inquiry to look again at the conviction, said: "As far as I am concerned, the conviction was a gross miscarriage of justice and the efforts the police and Crown Office are making to locate other Libyans who may have colluded in the bringing down of Pan Am flight 103 amount to little more than eye-wash.

"In other words, I think it's a thoroughly cynical attempt to deceive the public into thinking the conviction was justified."