Nagasaki's mayor says it was an "outrageous act" which ignored the feelings of people of the city.

The test on the Trident nuclear missile system was carried out in Nevada.

Mayor Iccho Ito says the participation of Britain for the first time in a sub-critical test might trigger a series of nuclear tests in other countries, the Mainichi Daily News reports.

Sub-critical means no critical mass is formed so the explosion doesn't result in a nuclear chain-reaction. The UK has shared test results before but not taken part in US tests in the past.

"It was an outrageous act that is totally against the tide of international movement. They ignored the feelings of people who had been atom-bombed," Mayor Ito said.

The test was conducted underground inside a metal container using a small amount of plutonium and explosives, according to the US Department of Energy.

Mayor Ito added: "Other nuclear nations may think about conducting tests of their own, which will lead to the end of the Comprehensive Test Ban Treaty (CTBT) and, ultimately, the resumption of full-scale tests."

Hiroshima Mayor Tadatoshi Akiba also criticised the US and Britain: "They betrayed people all over the world who are working hard to eliminate nuclear weapons. I feel like I time-warped 60 years back when everyone was trying to develop an atom bomb."

A spokeswoman for the Ministry of Defence told Ananova the test was to ensure the safety and reliability of the Trident nuclear missile system.

Story filed: 10:05 Friday 15th February 2002