Foreign policy provisions in the Lisbon Treaty are the same as those rejected in the failed European Union constitution, according to a British parliamentary report published toay.
The findings are problematic for the UK government because they have decided against a referendum on the treaty but had promised one on the proposed constitution.
They could also add to the No campaign arguments in Ireland, which is the only member state that will be holding a referendum.
The treaty has been criticised for effectively being the constitution by another name with cosmetic changes. Yesterday Green Party members refused to give the treaty their official endorsement contrary to the wishes of the party leadership.
Labour Party spokesman on European Affairs Joe Costello said the party's uncertainty risked "playing right into the hands of the No campaign".
"Now, a junior partner in government is at sixes and sevens, where their parliamentary party is apparently in favour of the treaty, but where the Party itself, after yesterdays proceedings, actually has no position," he said.
The constitution was rejected by voters in France and Holland in 2005. If Irish voters reject the treaty it will mean EU leaders will need to make a third attempt to form an agreement they say is necessary for the efficient adminstration of an expanded EU.
Anti-treaty campaigners say the proposed to changes to majority voting are a threat to national sovereignty while defence proposals threaten Irish neutrality.
Today's report by the House of Commons Foreign Affairs Committee which found the framework for foreign policy in the treaty was no different from that in the constitution supports their argument.
"We are concerned that the government risks underestimating, and certainly is downplaying in public, the importance and potential of the new foreign policy institutions established by the Lisbon Treaty," the committee said.
Separately, Kieran Allen of the anti-treaty web site Voteno.ie said the Government's retain records the internet activity of Irish residents for three years was hypocritical.
The Irish Timesreported yesterday that the Department of Justice intends to the controversial EU data retention directive with a month - making it one of the first member states to do so.
Dr Allen, a UCD lecturer and prominent left-wing opponent of neo-liberalism, said the Government promotes the Charter of Fundamental Rights contained in the treaty while launching an "astounding attack on civil liberties" through the directive.
He said the it allows for the gardaí to access the internet records of citizens at any time without a court order.
Additional reporting PA