However Mr Hague also said it could not be a substitute for an official poll held by the government.

His comments come as senior members of the Conservative Party - traditionally eurosceptic - have been floating the idea of a referendum paid for with private funds.

So far, prime minister Gordon Brown has resisted the calls for a vote on the final EU treaty.

The calls started almost as soon as the outline for the document was set out in June - with the whole treaty supposed to be finalised by the end of the year.

Mr Brown has been arguing that a referendum is not needed because Britain's concerns about the treaty - including on a citizens' rights charter and criminal justice matters - have been dealt with in specific opt-outs.

But several conservatives as well as some members of Mr Brown's Labour party are pressing the prime minister to make good on a previous promise by the government to hold a referendum on the original EU constitution.

The pledge was made before French and Dutch voters rejected the EU constitution in mid-2005 - shock votes that eventually led to member states reworking the original text to produce the 'Reform Treaty.'

Since then several politicians have said that it is largely the same as the old constitution.

Writing in the Sunday Telegraph, Labour MP Gisela Stuart, a key former member of the body that drew up the EU constitution five years ago, said it is an issue of "trust."

"The Government undermined trust by its original handling of the EU constitution," she wrote.

"It should never have pretended that it was just a 'tidying up' exercise, and it has continued on a similar line with the new treaty. Well, it was rubbish then and it is rubbish now."

So far, of the 27 member states, only Ireland is definitely to have a referendum on the treaty.