Prime Minister Gordon Brown has been accused by the Tories of trying to push the EU Treaty through "on the quiet".
Shadow foreign secretary William Hague renewed calls for a referendum to be held on the deal, insisting it meant a major transfer of sovereignty from the UK.
Only 10 out of the 250 proposals had changed from the former constitutional treaty - which the Government had pledged to put to the vote before it was ditched, he added.
Mr Hague was speaking as he launched a pamphlet claiming to explain the contents of the new treaty in "plain English".
It says powerful positions are being created in the EU, with a President and a "high representative" who is a effectively a foreign minister.
The union will also be given the legal status to sign international treaties, while Britain is losing vetoes in some 60 policy areas.
Mr Hague said that once Parliament returned from the summer recess it would only have nine working days to consider the treaty before it was passed.
He also suggested that the document had been made deliberately "unreadable" in order to stifle concerns over the content.
"I think in a way (Gordon Brown) wants to get this out of the way with as little public attention as possible," he said. "Certainly they want to get it through on the quiet."
A number of prominent European politicians have estimated that the new agreement contains between 90% and 98% of the measures in the original constitution document - which was abandoned in 2005 after failed referenda in France and Holland.
