Lord Bell does not deny claims his firm asked PM to complain to China about copyright infringement on behalf of James Dyson

Lord Bell has defended David Cameron's decision to raise his client's business concerns during a state visit by the Chinese prime minister, after he was reportedly asked to do so by Bell's lobbying company.

As the government faced criticism for allowing lobbyists to get too close to ministers, Bell did not deny claims that his lobbying and public relations firm contacted Downing Street to ask the prime minister to complain to Wen Jiabao about copyright infringement in China of products designed by Dyson, a client of Bell Pottinger.

"What happened with the copyright issue with the Chinese was in the national interest," Bell said.

Senior Bell Pottinger executives were caught on film by undercover reporters from the Bureau of Investigative Journalism pitching their services to fake representatives of the government of Uzbekistan. They said they managed to get the prime minister to raise Dyson's copyright issue with Wen during a state visit in June 2010.

"We were rung up at 2.30 on a Friday afternoon, by one of our clients, Dyson," Tim Collins, managing director of Bell Pottinger, said. "He said, 'we've got a huge issue. A lot of our products are being ripped off in China'.

"On the Saturday, David Cameron raised it with the Chinese prime minister … He was doing it because we asked him to do it and because the issue was in the wider national interest. In terms of very fast turnaround and getting things done right at the top of government, if you've got the right message, we can do it."

Collins is a former shadow secretary of state for education and earlier in his career he worked alongside Cameron and the future chancellor, George Osborne. During the meeting, he boasted about his access to these two and to the prime minister's policy chief, Steve Hilton, and Downing Street's chief of staff, Ed Llewellyn.

A spokesman for Cameron said the prime minister had not been asked whether he or other ministers had spoken to representatives of Bell Pottinger about Dyson, or whether these concerns had been passed onto the Chinese government. Downing Street denied there was any "undue access".

"It is wholly unsurprising that, in a conversation with the Chinese, we might talk to them about intellectual property rights," said the spokesman. "I think you would be surprised if we did not. In conversation with foreign governments, we often talk about business issues."

He also launched a surprise attack on the lobbying industry and dismissed the possibility that Bell Pottinger or other lobbying companies had influenced government. "It is simply untrue to say that Bell Pottinger or any other lobbying company influences government," he said.

Hiring a lobbying company could be a waste of time, he indicated, saying it would be more productive to companies if they made direct contact with ministries or Downing Street instead of trying to influence policy through lobbyists.

"In my experience of the civil service, the official process is the better one to pursue," he said. "If companies want to spend money on lobbyists, that is a matter for them."

A spokesman for Dyson would not comment on whether the firm had asked Bell Pottinger to push the copyright infringement onto the agenda of the UK/China talks. "We do occasionally work with Bell Pottinger but our main conduit to the government is via its business advisory group, of which James Dyson is a member," he said.

The shadow Cabinet Office minister, Jon Trickett, accused the government of being "too close to corporate interests". "These are very serious allegations involving a former member of the Conservative frontbench as well as some of David Cameron's closest confidants inside Downing Street and his cheerleaders in the media," said the Labour frontbencher.

"We have been calling on the government to implement a statutory register of lobbyists. We need reform to ensure that there is no question of the rich and powerful buying access to the prime minister and his advisers."

The prime PM has warned that lobbying is a scandal waiting to happen. Government proposals for a statutory register of lobbyists, which were due to be published last month, are expected after Christmas.

Of 115 MPs questioned by Populus over the past four weeks, 62% agreed that a statutory register would help the democratic process, compared with 13% who said it would not. But just 12% said that public relations professionals were a "hindrance" to their work as MPs, compared with 57% who said they were not.

Forty-one of the MPs questioned (36%) said that occasions when they socialised with lobbyists were "an important part of an MP's week", against 33 (30%) who disagreed.

Bell, a former communications adviser to Margaret Thatcher, is furious about the methods used to secure the story and has filed a complaint with the Press Complaints Commission which claims that there was no proof of impropriety, and that the same information could have been established without undercover reporting.

The Bureau of Investigative Journalism confirmed Bell offered the reporters an interview prior to publication, although he would not allow it to be recorded. Bell said in a statement the story was "an attempt by unethical, underhand deception to manufacture a story where none exists".

Iain Overton, the director of the BIJ, said the undercover operation was warranted because they could not have gained the information by other means and it was in the context of "a national debate about lobbying, which as Cameron has stated, could be the next big scandal".