Pro-Europe MPs face sabotage campaign to force a referendum on EU constitution

Millions of leaflets will be sent to voters in the constituencies of 101 Labour and 30 LibDem MPs with majorities under 5,000.

They will accuse the MPs of treating the public like "fools".

Organisers of the ReferendumList.com campaign say even a small backlash could unseat many of the anti-referendum MPs.

All have been warned about the leaflet blitz and invited to change their position.

Details of the campaign emerged as Gordon Brown prepared to sign Britain up to the controversial EU Reform Treaty today, despite Tory claims that he has no mandate.

Shadow Foreign Secretary William Hague said if the Prime Minister reneged on his party's pledge to hold a referendum "no one will trust him on anything else".

The Prime Minister will miss the official signing ceremony in Lisbon - pleading a "diary clash" with an appearance before senior MPs in Westminster - but will add his name later in the day.

The fudge has prompted ridicule by both supporters and critics of the EU.

Mr Brown insists the treaty is an "amending" document and not a new constitution.

But a string of other EU leaders have admitted it is almost identical to the proposed 2005 constitution, on which Labour promised a referendum before it was rejected by voters in France and Holland.

The new treaty will still create an EU president, give the EU its own 'legal personality', like that of a country, end Britain's right to veto policy in more than 40 areas and strengthen EU courts.

The attack on the anti-referendum MPs is being funded by Tom Kremer, an entrepreneur who popularised the Rubik's Cube, among others.

Stuart Coster, director of the Democracy Movement pressure group which is organising it, said: "This will make the revised EU constitution treaty a very personal, matter for those MPs who refuse to honour their manifesto promises.

"They face being named and shamed to thousands of voters."

Even without a referendum, ministers face a bitter battle in Parliament to get the treaty approved.

Foreign Secretary David Miliband has promised that the Bill bringing it into law will be carefully scrutinised - but sparked anger by indicating that MPs will not be able to propose amendments.

A sign of the hostility he will face came from Labour's Michael Connarty, chairman of the European Scrutiny Committee, who accused ministers of being "frit" about a full debate.

The European Commission is to set up its own radio station, subsidised at a rate of £11,500 a day, to run programmes "from a European point of view" to up to 20million listeners.

It will broadcast initially in English, French, German, Spanish and Polish, but by 2012 the number of languages will have reached 23.