Cameron's new entente cordiale hailed in 'radical defence' deal

At the UK-France summit in London yesterday, the Prime Minister described it as "big, bold and radical" while President Nicolas Sarkozy said it demonstrated an unequalled measure of trust.

The deal was greeted with suspicion by some senior Tories, however, who warned that Britain and France had divergent strategic interests and questioned whether the French could be trusted to come to the UK's aid in a crisis.

The agreement will see the creation of an integrated carrier force with the two countries co-ordinating the refit programmes of their single remaining carriers to ensure that from the 2020s onwards at least one ship will always be available for joint operations.

British and French troops will train together in a Combined Joint Expeditionary Force capable of deploying round the world and the two countries will develop a new joint unit for testing their nuclear warheads, without the need for test firings which are banned under international treaty.

The agreement also opens the way to greater co-operation on programmes to develop new missiles, submarine technologies, satellite communications and unmanned aerial drones.

The two countries will also pool resources to cut the cost of operating the new A400M transport aircraft, which they are both acquiring, while RAF air tankers may be available for the in-flight re-fuelling for French fighter jets.

Mr Cameron said the agreement would let both countries enhance their defence capabilities at a time when they were seeking to reduce costs and he denied it represented a diminishing of national sovereignty, stressing both countries would retain the right to decide independently when to deploy their forces on military operations.

"This is not about a European army. This is not about sharing our nuclear deterrents," he said.

"It is about defending our national interest. It is about practical, hard-headed co-operation between two sovereign countries. This is the start of something new, not an end in itself." President Sarkozy played down suggestions France would not be prepared to deploy its carrier in support of British interests if the UK vessel was in dock. "If you, my British friends, have to face a major crisis, could you imagine France simply sitting there, its arms crossed, saying that it's none of our business?"

However Tory MP Bernard Jenkin, a former shadow defence secretary, said the French had "a long track record of duplicity" and would always put their own interests first, later telling the Commons: "We cannot have a strategic fusion with a country which has historically – and still has – diametrically different strategic objectives on the world stage."

Defence Secretary Liam Fox disclosed that American Defence Secretary Robert Gates had raised concerns about the implications of the new treaty on nuclear co-operation for the 1958 US-UK mutual defence agreement, but he had been able to allay concerns.