TONY Blair has conceded he faces a tough fight to sell the EU constitution to a sceptical British public in a referendum.

But the Prime Minister insisted voters would be won round once they were told the truth about the deal.

However, the Tories branded the constitution - thrashed out in Brussels on Friday night - as "a gateway to a country called Europe".

Robert Kilroy-Silk, the talk show host-turned-UK Independence Party (UKIP) Euro MP, likened Mr Blair to Neville Chamberlain - prime minister at the start of the Second World War - and his appeasement of Hitler.

Mr Blair was on television after flying back from Brussels with a deal he said was a success for Britain and Europe.

The 300-page document still needs to be approved by all 25 national parliaments, and by referenda in at least six member states, including Britain.

Opponents challenged Mr Blair to call the poll immediately. Yesterday, he refused to do that, but signalled MPs could vote on the constitution before the next General Election.

The constitution does not have to be ratified until the end of 2006. Mr Blair said there would be a parliamentary debate before a referendum.

He said he had secured all his "red lines" in Brussels over the key areas that made Britain a nation state.

He accepted opinion polls indicated opposition to the constitution but said that was because the public had not been told the truth about it.

"This is going to be a fascinating political battle because it will be a battle between reality and myth,'' he said.

He said the Tories and UKIP wanted the referendum now because they feared that the longer the debate went on, the more their myths would be exposed.

Speaking on BBC1's Breakfast with Frost, he said: "This treaty gives us the chance to play a vital part in decision-making at the heart of the EU, whilst it protects completely our right to set our taxes, run our foreign policy and defence, and do the things that people want us to do.''

To get out now or marginalise Britain would be an "extraordinary act of foolishness", he said.

Shadow Foreign Secretary Michael Ancram said: "It is going to be a constitution which has supremacy over our constitution, over our laws, and this is something which we believe is highly damaging to the interests of this country, so we'd oppose it for that reason.