The strike by London Underground staff has been slammed by the prime minister as "utterly unnecessary".

Tony Blair used his Blackpool press conference to appeal to the RMT to call off its dispute with Tube bosses.

He claimed that the union hardliners were losing support.

"The strike in London is totally and utterly unnecessary," Blair told journalists.

His comments came as the union signalled it was considering a third one-day walk out.

"I hope the union leadership will realise it has no support among the public at large. I suspect it has declining support among their own membership. It won't make any difference to the way that either the government conducts its policy or the Underground is run."

"We've just got to set out our position very clearly and see it through."