The government has refused to give MPs access to papers on international negotiations about copyright enforcement on the internet and at national borders.
Junior business minister David Lammy said he could not put documents about the Anti-Counterfeiting Trade Agreement (ACTA) in the House of Commons Library, because other countries wanted to maintain secrecy.
Lammy said he was "sympathetic" to calls for more transparency and had told his officials to press the point at the talks, but added: "Disclosure of any documents without the agreement of all our ACTA negotiating partners would damage the United Kingdom's international relations.
"This would harm our ability to protect, promote and secure an outcome in the UK's interest, and the premature release of documents that are not agreed and not fully developed may also have a negative effect on the government's reputation."
The secrecy surrounding ACTA has prompted speculation the agreement will be favourable to the music and film industries, whose lobbyists are party to the discussions.
The European Commission, also involved in negotiations, responded that "ACTA will not go further than the current EU regime for enforcement of intellectual property rights".
It also rejected claims that ACTA will mean border guards will search digital devices for pirated material.
"EU customs, frequently confronted with traffics of drugs, weapons or people, do neither have the time nor the legal basis to look for a couple of pirated songs on an iPod music player or laptop computer, and there is no intention to change this," the Commission said, claiming talks on border measures concerned controls on conterfeiting.
In December, EuroISPA, an ISP trade association, said the ACTA talks could be used to spread disconnection policies for online copyright infringers, already proposed in the UK under the Digital Economy Bill.
"If some of the proposals currently under discussion in the context of these trade negotiations are adopted, ISPs will have to implement 'graduated response' measures," EuroISPA said.
Others have argued that ACTA will make little difference to copyright enforcement in the UK. The true effect should be clear when the talks are completed this year and the final agreement published. ®