The launch of the government's pro-European campaign is an attempt to cover up its divisions on the single currency, Tory leader Iain Duncan Smith has said.
Pro-Europe campaign is a 'smokescreen'
He argued that "no amount" of joint press conferences staged by the prime minister and chancellor would convince the British people they were united on the euro.
Tony Blair and Gordon Brown are set to issue a pro-European rallying call at a news conference in Downing Street on Tuesday.
The Tories are publishing a dossier detailing the "grave dangers" of euro membership "glossed over" by Mr Brown, but contained in the Treasury's 18 studies on the issue.
It was a political decision taken by the chancellor in order to preserve the unity of his own party against the very deep divisions that they always have on this particular issue
But Mr Duncan Smith accused the government of "running scared" of public opinion on the euro, stressing: "They have come up with the most absurd mess.
"This is an elaborate smokescreen to hide the fact that there is only one test that matters to either of them, and that is whether they can win a referendum."
The chancellor's five economic tests, on which he will assess whether Britain is ready to join the single currency, could be interpreted in "almost any direction", said Mr Duncan Smith.
"I don't believe the government is in any way going to be having a referendum because the truth is they are running scared of public opinion."
Mr Duncan Smith likened the situation to the controversy surrounding the drafting of a new EU constitution.
He said the government would not allow the British people to have a say on this either "because they are scared they will say no".
"This is the point about the government - they only ever ask the British people to have a decision when they believe they know what that decision is going to be," he told BBC Breakfast.
Shadow foreign secretary Michael Ancram said the euro was "wrong for this country, both politically and economically".
"I will oppose a single currency in a referendum and I hope that the British people will too," he told BBC Radio 4's Today programme.
"As the chancellor said yesterday, this is an irreversible decision. This isn't just for Christmas, it's forever."
He added: "What we saw yesterday was essentially not an economic decision. It was a political decision taken by the chancellor in order to preserve the unity of his own party against the very deep divisions that they always have on this particular issue."
On Monday, shadow chancellor Michael Howard said Mr Brown's "not yet" verdict on euro entry was the "beginning of the end" for Mr Blair's government.
He accused Mr Brown of fiddling and distorting the evidence and demanded to know why Britain should accept the "straight jacket" of a singe European interest rate.
"This whole exercise has been an exercise in deceit," Mr Howard told MPs.
"The deceit that they have the national economic interest at heart, the deceit that they want an objective assessment of what this country needs, the deceit that they are united."
The shadow chancellor argued that the government had substituted a policy of "prepare and decide" with one of "hope and pray".