London's new mayor Boris Johnson has pulled out of a global campaign group that calls for nuclear disarmament, saying the city's membership was "not a priority", his office told AFP Wednesday.

A spokesman confirmed a claim by British lobbyists the Campaign for Nuclear Disarmament (CND) that Johnson had withdrawn London from the United Nations-backed Mayors for Peace initiative that opposes nuclear proliferation.

CND chairwoman Kate Hudson said the decision was "appalling", despite being aware that Johnson, from the main opposition Conservative Party, backed the renewal of Britain's nuclear capability.

A spokesman for the mayor said: "Whilst there may be debate about the proliferation of nuclear weapons, membership of Mayors for Peace is not a priority for the new administration."

Instead the mayor, who ousted Labour left-winger Ken Livingstone in a May 1 vote, was committed to tackling "domestic issues of major importance to Londoners" like safer streets, improved public transport and living standards.

"The mayor is also committed to value for money for London taxpayers and it is a much better use of his and his team's time to focus on the important day-to-day issues that need to be addressed, which is what he was elected to do."

Mayors for Peace was founded by the mayor of the Japanese city of Hiroshima, which with Nagasaki were flattened by US Air Force atom bomb strikes in 1945, killing hundreds of thousands and ending Tokyo's involvement in World War II.

There are currently 2,277 member cities in 129 countries.

CND chairwoman Kate Hudson said that they found it "appalling that the mayor should reject participation in an international body committed to the global abolition of nuclear weapons."

Previous Conservative governments had supported British participation in the nuclear Non-Proliferation Treaty but Johnson's decision suggested he was "retreating" from its ultimate goal of universal nuclear disarmament, Hudson said.

"This decision is insulting to the people of Hiroshima and Nagasaki and the work of their Mayors for global peace, and goes against the views of the majority of the British people, who support global nuclear disarmament."