The newly negotiated EU constitution demolishes the myths spread during the months of haggling, Tony Blair has told MPs as he starts selling the new deal.
Blair says he will lead the referendum campaign
The prime minister said it showed the EU was "not a superstate, not a federal state but a group of nations".
Mr Blair said the treaty protected UK control of tax and other key issues.
But Tory leader Michael Howard called the document "bad for our democracy, bad for jobs and bad for Britain" and said Mr Blair was spreading myths".
The prime minister says the UK will only sign up to the constitution if the public backs it in a nationwide referendum.
Opinion polls suggest that might prove difficult at the moment - and a number of Labour MPs oppose the deal.
Mr Blair began the battle to win over the sceptics on Monday but said "myths" were being put out by those who questioned whether Britain should be at the heart of Europe.
Citing the trade and aid benefits of EU membership, he said 3.5m British jobs relied on its membership.
He accused opponents of the constitution of putting EU successes at risk for "a narrow
nationalism" which did not have Britain's true interests at heart.
Mr Blair said qualified majority voting was being extended where needed but vetoes remained on key areas and Britain could opt out of measures affecting asylum, immigration and criminal procedure laws.
He also insisted the new Charter of Fundamental Rights would also not affect British industrial laws.
But the Tory leader said the president of the European Court of Justice had offered no guarantees on that claim and he argued the charter was "a case
study in government surrender".
Mr Howard lampooned the prime minister as the "great myth-maker" as he promised to take part in a cross-party campaign against the treaty.
Key British powers were being surrendered to Brussels when in fact people wanted power back from the EU, he said.
There were 43 new policy areas where majority voting would mean measures being "imposed" upon Britain.
"Let's have none of this nonsense of the referendum being about being in or out of Europe," continued Mr Howard. "It is about the kind of Europe we want to see."
He said Mr Blair had failed to deliver on his previous promises of leadership of the pro-European cause.
"The prime minister's definition of leadership is to press the mute button," he joked.
Liberal Democrat Charles Kennedy said a "yes" vote in the referendum would not be won if the campaign was "spun from Downing Street".
He welcomed the "compromise" deal, saying the constitution was not a moral crusade but a way of making the enlarged Europe work effectively.
Mr Kennedy warned: "We cannot, any of us, deny the growth of Euroscepticism both in this country and through the EU."
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The gap between the views of the political elites and voters made the referendum especially essential, he argued.
Some Labour MPs such as the former Europe minister, Keith Vaz, have echoed Lib Dem calls for a more vigorous pro-European campaign.
But anti-constitution Labour MPs are setting up a group under the banner "Labour against a
On Sunday, UK Independence Party (UKIP) MEP Robert Kilroy-Silk said the new treaty did nothing for Britain.
"It's appeasement," he said, adding: "This is the beginning of the end of Britain as a nation state governing itself."