The MEP in charge of steering a controversial anti-piracy treaty through the European Parliament has "strongly" recommended that MEPs reject the agreement.
British Labour MEP David Martin said there were "serious flaws and concerns" about the way the Anti-Counterfeiting Trade Agreement (Acta) could be interpreted and implemented.
The international treaty - signed by 22 of the 27 EU member states, as well as countries such as the US, Japan and Morocco - is designed to help countries around the world tackle large-scale intellectual property theft.
It lays down a framework for enforcing existing copyright laws globally and also seeks to curb the trade of counterfeited physical goods.
But opponents fear it will harm civil liberties and freedom of expression on the internet.
Mr Martin listed several "key" problems with the text, including a lack of detail on the definition of commercial scale versus private use.
"Freedom of internet is highly valued by our citizens and we interfere with that at our peril," he warned.
However, Trade Commissioner Karel de Gucht insisted that "there is nothing to fear in this agreement", during the debate in the European Parliament.
He said fears about the impact of Acta were unfounded because the treaty introduces no new laws.
"Since our freedoms are not threatened by our current laws our freedoms will not be threatened by Acta," he said.
He warned that rejecting the international agreement would be a "setback" against the protection of intellectual property.
Cure not kill
But an overwhelming majority of MEPs remained unconvinced.
Members from the parliament's social democrat, liberal, Green and far-left groups lined up to make clear their opposition to the treaty, pledging to vote against it on Wednesday.
They argued that the measures are disproportionate, risk fundamental rights and freedoms and that the text is too vague, leaving it too open to interpretation.
Representatives from four key parliamentary committees also set out their reasons for recommending that the parliament says no to the deal.
Several MEPs from the centre-right EPP group criticised the European Parliament for holding a vote on Acta before the European Court of Justice deliver its ruling on the legality of the treaty.
However they were accused by some of wanting to postpone the vote in the hope Acta would be passed further down the line.
German EPP MEP Daniel Caspary responded: "We want to treat Acta, not kill it; that is the difference between you and I."
The fate of Acta will be decided in a vote on Wednesday, as the treaty cannot become law in the EU unless it is approved by the European Parliament and all member states.
This is because the Lisbon Treaty gave the European Parliament the power to reject or approve international treaties involving the EU.
Several key countries, including Germany and Poland, have backed away from the deal amid large-scale protests in several European cities.
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