A spokesman for the Prime Minister said: "We would, of course, welcome all progress that can be made with regard to the investigation."
He said Mr Cameron had raised the Lockerbie issue on a number of occasions with the Libyan government, most recently when he visited Tripoli in February.
The move by the Libyans has been described as a "significant step" by Frank Mulholland, the Lord Advocate, and it is hoped it will open the way for Scottish detectives to interview Abdullah al Senussi, the former head of Libya's intelligence agency, who is incarcerated in Tripoli, accused of ordering massacres during the revolution two years ago.
The decision by the Libyan government is a U-turn, as earlier this year it made clear it regarded the Lockerbie case as "closed".
Meantime, British relatives of the bombing victims are to consider making another appeal against the conviction of Abdelbaset Mohmed Ali al Megrahi, the only man found guilty of the atrocity.
Members of the UK Families Flight 103 group will meet lawyers in the New Year to discuss whether to apply to the Scottish Criminal Cases Review Commission, according to Dr Jim Swire, whose 23-year-old daughter Flora died in the December 1988 tragedy.
"The intention of some members is to meet with lawyers in January and discuss the best options, the best way to get the truth," he said.
"It's a disgrace that we have to wait 25 years to get the truth that should be available from our governments," added Dr Swire.
On Saturday, relatives of the victims will hold 25th memorial services at Lockerbie, Westminster Abbey and the Arlington National Cemetery in Washington DC.
Some 270 people died in Britain's worst terrorist atrocity. Most were Americans.