A voluntary register of lobbyists is to be published today amid accusations from transparency campaigners that it only features a small proportion of the controversial industry.
The UK Public Affairs Council (UKPAC) is to publish details of firms and individuals who work in lobbying alongside lists of their clients.
But critics claim that the vast majority of lobbyists - up to 90% - are shunning the register and so will not be included.
The move follows years of demands for greater openness about who is trying to influence Government policy for whom.
MPs have raised concerns about the perceived "privileged access and disproportionate influence" wielded by lobbyists operating in the shadows.
The Public Administration Select Committee has called for a statutory register, which the Government is committed to introducing.
The UKPAC was set up by industry bodies the Association of Professional Political Consultants (APPC), the Chartered Institute of Public Relations (CIPR) and the Public Relations Consultants Association (PRCA).
Members of those organisations who meet a definition of lobbying set out by the UKPAC are required to put their details on the register.
Campaign group the Alliance for Lobbying Transparency claimed that as few as 10% of lobbyists would be on the register when it goes live today.
Spokeswoman Tamasin Cave said there were no law firms, management consultants, accountancy firms, charities or think tanks on it.
"This new register is no more than a PR stunt from the PR experts," she said.
"With so few lobbyists registered, and so little information revealed, the public and parliamentarians still don't know which outside interests are wielding, in David Cameron's words, 'unhealthy influence'.
"Only a statutory register of lobbyists can force the £2 billion influence industry out into the open, so that we can really see who is lobbying whom, and crucially which policies they are trying to influence and how much money they are spending.
"The Government must act on its promise now to introduce a statutory register."