The independent MP Martin Bell added his backing, alongside seven Labour MPs and the pressure groups Charter88 and the Electoral Reform Society.

Martin Bell: "Losers must feel fight was fair"

The Tory spokesman on constitutional affairs, Dr Liam Fox, said: "In the current Orwellian political climate, to have seven Labour members willing to put their names down is a matter of singular political coverage."

Greatest support for the call on the government to establish an independent commission to draw up a referendum act came from the Tory benches.

Dr Fox said if such proposals were not in the Queen's Speech, the Conservatives would put down a bill in the Lords.

He said referendums needed similar regulation to elections and stressed this was not a party political campaign.

At a news conference attended by three journalists, he added: "The only hope is that pressure will be brought by the media and the profile of this issue will be raised.

"Especially after what Lord Neill said about the Welsh referendum, if there wasn't a water tight case for reform before, there is now."

Mr Bell, the MP for Tatton, said it was a question of giving "legitimacy" back to referendums after the narrow victory for the government-backed Yes campaign in Wales.

"The losing side has to feel it was fairly conducted.

"I am keeping some strange company on this issue, but on this the Tories happen to be right.

"The current situation is profoundly undemocratic. We do not conduct our general elections in this manner and we must not conduct our referendums in this matter."

Mr Bell pointed out both he and the various campaign groups would be on the opposite sides of the argument from the Conservatives in a referendum on proportional representation.

Liam Fox: "Not a party political campaign"

Dr Fox said this showed the apolitical nature of the campaign. Despite 65 Tory MPs signing the "reasoned plea" being put before the government, the party had chosen not to instruct its members to do so.

He added: "The strongest support comes from people completely outside the main political system, such as the Lords of Appeal and the political scientists who have signed up.

"It is not just a parliamentary feeling - it goes much wider."

The "reasoned plea" calls on the House Speaker to set up an independent commission, which would report within three months. It then asks the government to hold any future referendums in accordance with these rules.