The Anti-Counterfeiting Trade Agreement (ACTA) was rejected by committees responsible for overseeing its legality, economic impact and ramifications on civil liberties.
ACTA has so far been signed by 22 member states, including the UK, but the European Parliament will not make a decision on whether to ratify the legislation until July.
The agreement covers the counterfeiting of physical goods, but campaigners have particularly expressed concern about the anti-internet piracy proposals, such as the potential introduction of fines and imprisonment for online copyright infringement.
Ever since the initial draft of the act was released on WikiLeaks in 2008, civil liberties campaigners have warned that it represents a potential threat to freedom of speech online, and claimed that the important issue was being debated in secret.
ACTA has also been likened to the Stop Online Piracy Act (SOPA) in the US, which was dropped earlier in the year after a broad protest campaign.
The EU Committee on Legal Affairs (Juri), Committee on Civil Liberties (LIBE) and the Committee on Industry, Research and Energy (ITRE) have now all expressed "opinions against ACTA".
Their views will be taken into account by the Committee on International Trade (INTA), which is due to make the final recommendation to the European Parliament.
ACTA's future already looked precarious, after David Martin, INTA's appointed rapporteur on the act, recently criticised the legislation.
In April, he said: "The intended benefits of this international agreement are far outweighed by the potential threats to civil liberties."
INTA will vote on the act on June 21.
The Open Rights Group welcomed the decision by the Juri, LIBE and ITRE committees to vote against ACTA.
"This is a strong signal that more and more MEPs recognise ACTA is so badly flawed, in so many ways, that it must be rejected," said Peter Bradwell of the Open Rights Group.
"Together the votes are a protest against an unnecessarily imbalanced and ill-considered treaty. There is still a long way to go before ACTA is finally defeated.
"The final vote in the European Parliament is in a month's time. We need to continue to convince more MEPs that ACTA puts our privacy and freedom of expression at risk and is an affront to democratic principles."
In a statement, the UK government's intellectual property office said that it was still in support of ACTA, but would respect whatever decision is reached.
"The UK supports the aims of ACTA and continues to support a global co-ordinated approach to intellectual property enforcement," said the IPO in a statement.
"We are watching the developments at the European Parliament carefully and respect whatever decision they make regarding ACTA."