Mr Tony Blair has acknowledged he faces a tough fight but insists he can and will win the British referendum on the new European constitution, now expected in 2006 writes Frank Millar in London.
The United Kingdom Independence Party (UKIP) yesterday likened Mr Blair to Neville Chamberlain, Britain's prime minister at the start of the second World War, and accused him of appeasement, while the Conservative leader, Mr Michael Howard, challenged him to hold the promised referendum immediately.
However, while confirming that MPs would be asked to approve the constitution before the next general election, Mr Blair signalled he was in no hurry to hold a referendum which two fresh opinion polls yesterday suggested he would lose.
Instead, he returned Conservative and UKIP fire, accusing them of running scared of what promises to be a fierce and protracted debate he says will be "a fascinating political battle between reality and myth".
Mr Blair won a significant public endorsement from former Conservative deputy prime minister, Lord Heseltine, while the Liberal Democrat leader, Mr Charles Kennedy, anticipated early talks with Mr Blair about the scope and direction of the pro-European campaign for a Yes vote.
While the Conservatives accused Mr Blair of opening "a gateway to a country called Europe", Lord Heseltine supported Mr Blair's own view that he had scored "a significant victory" over the Franco-German Alliance.
"If he (Mr Blair) hadn't stood out, it is very possible that the Europeans would have gone on in major areas like tax harmonisation, defence and foreign policy in a way that would have been difficult for the United Kingdom. We would have been excluded from that process," Lord Heseltine told Sky News. And he also backed Mr Blair's assertion that EU enlargement and Friday's agreement on the constitution has effectively shut the door on "a federal Europe".
Whereas President Chirac of France suggested the constitution would lead to "a federation of states but also of peoples", the British Foreign secretary, Mr Jack Straw, also insisted it actually "ends any possibility of the EU becoming a federal superstate - it cannot happen".
And despite Mr Howard's assertion that Mr Blair's negotiating stance was "a put-up job", the prime minister claimed he had "won every single thing" his government had wanted to secure.
Speaking on the BBC's Breakfast with Frost programme, Mr Blair said: "In all those key areas that go to make up Britain as a nation state, if you like... we have won every single thing we wanted to secure.
"This treaty gives us the chance to play a vital part in decision-making at the heart of the EU, while 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."
Mr Blair also stressed he had not been "the isolated voice of Britain" on any issue during the Brussels summit, and having concluded "a good deal for Britain", argued that any attempt now to get out (of Europe) or marginalise British influence would be an "extraordinary act of foolishness".
Mr Blair also suggested that Mr Howard's pledge to re-negotiate the constitution and the terms of British membership of the EU would put the UK "next to the exit door".
However, when pressed if the same would be true for any of the other European states planning to hold referendums, Mr Straw told the BBC Radio 4's World this Weekend programme "No", adding that Britain, as one of the largest EU members, had "a particular role to play".
The scale of the political challenge confronting Mr Blair will be underlined again later today when rebel Labour MPs launch their own campaign group - Labour Against a Superstate.
In the Commons, meanwhile, Mr Howard will taunt Mr Blair over suggestions that he will delay the referendum by almost two years. Yesterday's ICM poll suggested that 57 per cent of Britons would vote No, and only 28 per cent Yes, if the referendum was held now.