Defeated Labour mayoral candidate Ken Livingstone has accused the government of attempting to "trample on Londoners" over its plans for a partial sell-off of London Underground.

Mr Livingstone broke his three-day silence following Frank Dobson's narrow victory by saying the election was now a question of whether the city should have a candidate forced on it that it does not want.

Opinion polls published since Mr Dobson won Labour's nomination, despite less people having voted for him in the party's controversial electoral college, have shown Mr Livingstone would win if he ran as an independent.

There has been mounting speculation as to whether the Brent East MP could declare an independent candidacy. On Sunday, the left-winger said he would "listen to Londoners" before deciding on his next move. He is not expected to announce any decision until next week.

In his statement about London Underground Mr Livingstone said if Labour did not scrap its plans for the sell-off, the mayoral election would become a referendum on Londoners' rights not to have a transport system and a mayor that they do not want imposed on them.

Mr Livingstone accused the government of attempting to "trample on Londoners" by foisting an "unsafe" transport system on them.

Mr Dobson is in favour of the government's plans for the public-private partnership for the Tube, while Mr Livingstone wants to keep it in public ownership.

He supports a bond issue to fund development of the London Underground, a scheme which would keep the system in public hands but critics warn could leave London millions in debt.

"If Labour does not unequivocally withdraw its plans for privatisation of the London Underground, the election on May 4 will be transformed into a referendum on the future of London," said Mr Livingstone in his statement.

"The issues will be the following: Will London have a transport system imposed on it that it does not want?

"Should London have a candidate imposed on it that it does not want?

"In other words, does London have the right to govern itself, or is devolution to be a charade?

"The future of the Tube was the defining issue in Labour's selection contest, and by backing me, the great majority of party members made clear their opposition to privatising the Underground.

"They simply reflected the overwhelming majority opinion in London. Labour must accept this verdict.

"Even at this late moment, the government should abandon the attempt to trample on Londoners by imposing on them a potentially unsafe transport system which has clearly been rejected by the overwhelming majority of the electorate."

Meanwhile Mr Dobson, speaking at a hustings on Wednesday, dismissed the bond scheme for the Tube supported by Mr Livingstone as "pie in the sky".

He said the "public-private partnership" was a way of making sure any transport investment scheme was properly managed and delivered on time.

A Labour Party spokesman reacted to Mr Livingstone's statement by saying: "Ken Livingstone should stop playing games and issuing demands he knows cannot and will not be met.

"It is for him to answer the question: will he do the principled and honourable thing and stick by his word and support Frank Dobson?"

Reacting to Mr Livingstone's comments, Liberal Democrat mayoral candidate Susan Kramer said that the Labour left-winger was not the only "flag bearer" for a publicly owned London Underground.

"Keeping the tube in public hands has been a Liberal Democrat policy for more than two years," she told BBC News Online.

"I was delighted when Ken was won over to that cause but it is wrong to suggest that he is the one and only flag bearer on that issue."