The US has removed its nuclear weapons from Britain, ending a contentious presence spanning more than half a century, a report will say today. According to the study by the Federation of American Scientists, the last 110 American nuclear weapons on UK soil were withdrawn from RAF Lakenheath in Suffolk on the orders of President George Bush.

The report's author, Hans Kristensen, one of the leading experts on Washington's nuclear arsenal, said the move had happened in the past few years, but had only come to light yesterday.

He described the withdrawal of the B-61 "freefall", or "gravity", bombs as part of a general strategic shift since the end of the cold war.

"The northern front is not very relevant any more for these deployments. The US nuclear posture is almost entirely focused on the southern region, in Incirlik [in Turkey] and Aviano [in Italy]."

Movements of the US arsenal are shrouded in secrecy. Kristensen said the first signs the bombs had left Lakenheath emerged in a US airforce document dated January 2007 on nuclear inspections.

The document lists inspections of US nuclear sites, but above an annexe listing emergency drills carried out at the sites, it notes "not applicable to Lakenheath".

Kristensen's report is posted today at fas.org/blog/ssp.

He says the removal of bombs from Lakenheath follows the withdrawal of nuclear weapons from Greece in 2001, and that removal of such weapons from two Nato countries in less than a decade undercuts the argument for continuing deployment in other European countries.The removal from Britain would reduce the US arsenal in Europe to about 250.

Once officially declared, it could defuse current tensions with Moscow and possibly trigger matching cuts in the Russian stockpile.

Kristensen said last night: "It's so puzzling why Nato goes about the reduction in total secrecy. Keeping this secret completely undercuts our foreign policy interests."

The FAS was founded in 1945 by former scientists on the Manhattan Project, which produced the first atomic bomb, as a means of spreading information about the dangers posed by the new weapons.

Paul Ingram, the executive director of the British American Security Information Council, said last night: "This is a win-win situation for Nato and disarmament, and for rapprochement with Russia. Nato's future and the transatlantic alliance is tied up with operations in Afghanistan far more than with ageing freefall bombs that have no military relevance."

Greg Mello, the head of a nuclear watchdog the Los Alamos Study Group said: "The nuclear weapons themselves don't serve any military purpose. They are mostly about cementing a political bond that ties Europe interests to US interests."

The FAS study is being published a few days after Kristensen published a leaked US air force internal report saying that most European bases where US nuclear weapons were stored had inadequate security. The report, which was ordered after the US air force lost track of six nuclear cruise missiles last August, found that "support buildings, fencing, lighting and security systems" were in need of repair.

In some cases, conscripts with less than nine months' experience were being used to guard the nuclear weapons. Elsewhere private security guards were used.

The report recommends that the US nuclear arsenal in Europe be consolidated to "reduce vulnerabilities". That would involve the withdrawal of significant numbers of US nuclear weapons.