Law firms that lobby on behalf of their clients will escape the provisions of the government’s lobbying bill, transparency pressure group Unlock Democracy said today.

The group said plans to force firms to declare whom they represent would exempt 80% of the lobbying industry, including law firms, from having to comply.

The government said the Transparency of Lobbying, Non-Party Campaigning and Trades Union Administration Bill will bring greater transparency to politics and fairness to political campaigning.

But transparency campaigners warned the limited statutory list of ‘consultant lobbyists’ falls short of government promises for a wider-ranging register.

Alexandra Runswick, director of Unlock Democracy, said: ‘The problem with lobbying is not the respectable lobbying consultants who abide by a code of practice and already work in a relatively transparent way; the problem is the more underhand activity, whether it is employed by consultants, thinktanks, law firms, in-house lobbyists or private individuals.

‘By establishing such a gaping loophole, the government will simply drive business away from lobbying consultants and into the arms of less reputable agencies.’ The lobbying industry has also dismissed the legislation as a bill that undermines the goal of increased lobbying transparency.

The Association of Professional Political Consultants (APPC) pointed to research undertaken in 2012 that found business ministers had 988 meetings with lobbyists – of which just two were with consultant lobbyists.

APPC deputy chair Iain Anderson said: ‘The government’s plans are likely to result in less transparency with fewer organisations and individuals actually having to register than under the current self-regulatory regime the lobbying industry operates.

‘We would welcome a statutory register but only one which means all professional lobbyists are included.’

In spite of the criticism, Andrew Lansley, leader of the House of Commons, argued that the bill continued the government’s commitment to transparency.

Consultant lobbyists will have to disclose details of their clients on a publicly available register, complementing the existing rules under which ministers and permanent secretaries publish all of their meetings quarterly.

No organisation excluding political parties will be allowed to spend more than £390,000 across the UK during elections. ‘From the beginning, this government has believed that sunlight is the best disinfectant,’ said Lansley.

‘This bill is about extending that transparency further to give the public more confidence in the way third parties interact with the political system.’