A referendum on whether the UK should join the euro would be "rigged" by Prime Minister Tony Blair, Tory leader William Hague has said.

Mr Hague, speaking on the latest leg of his Keep the Pound tour of Britain, said Labour's troubled selection process to find a candidate for London mayor had shown that the prime minister could not be trusted to conduct a fair poll on the single European currency.

"We have just been discovering how Tony Blair likes to rig elections in advance with every kind of bullying and gerrymandering and misinformation," Mr Hague told a rally in Woking.

"He would try to do the same thing in a referendum on the euro."

A crowd of between 400 and 500 gathered to hear Mr Hague's speech.

He said all the evidence suggested that Mr Blair had blocked Ken Livingstone's attempt to be Labour's mayoral candidate and foisted his own man, Frank Dobson, on Londoners.

Mr Hague said Mr Blair had also installed Alun Michael as the Welsh First Secretary despite the wishes of local people, effectively leading to Mr Michael's resignation from the post.

'Bullying'

He continued: "All this fixing won't work. Frank Dobson is just Alun Michael with a beard and even if the Labour Party don't have the courage to reject him then, come May, London will."

But he said events in Wales and London were just the start, with Mr Blair preparing the ground for a referendum on the euro, by "bullying" people into believing that abolishing the pound was inevitable.

He said the government was introducing a new referendum law "whose sole purpose is to build in a huge spending advantage to the pro-euro side of any future vote".

But Minister for Europe Keith Vaz, who has has offered to join Mr Hague's tour of the country to put the government's side of the argument on the euro, said the Tory campaign was damaging the British economy.

He told BBC News Online: "They're telling the rest of Europe: 'Don't engage with us, don't trade with us, we don't want to be involved with you'. That is very dangerous."