The leaders of Britain's biggest trade unions have called for Prime Minister Tony Blair to oppose the controversial 'Son of Star Wars' project.

The 18 union general secretaries said the National Missile Defence system (NMD), which would involve the use of RAF Fylingdales radar base, would be

"wholly inappropriate".

Those opposed to the US scheme include Bill Morris of TGWU, John Edmonds of GMB and Unison's Dave Prentis.

In a letter, they said: "This initiative will not make the world a safer place and will do immense damage to international treaties covering weapons of mass destruction. "It will also considerably undermine international confidence in treaties as a system of resolving problems, if the US is to set them aside when it feels expedient to do so."

US President George W Bush is currently meeting the leaders of European countries to persuade them NMD is a good idea.

Tony Blair has so far declined to state whether Britain would back the project, on the grounds the US has not yet made any firm proposals.

But Downing Street has repeatedly said it understands and shares US fears about the threat of a missile attack from "rogue" states.

Speaking at the Nato Summit in Brussels yesterday, Mr Blair said: "There are highly unstable states who are developing nuclear capability.

"We have got to look at all the different ways, including defence systems, that we can deal with that threat."

Updated: 10:33 Friday, June 15, 2001