Client lists of big lobbying companies show that the number of organisations using their services has leapt by a third since 1996. In the same period, the larger lobbying companies' staff numbers have risen by more than a quarter and turnover has increased by about a fifth. The boom will reopen the row over close links between Government ministers and certain lobbying companies. Dozens of former Labour Party staff have been employed by the lobbying industry since the last general election, and insiders admit that many are valued for their address books rather than their knowledge or experience.
Newspaper revelations last year of how some lobbyists had bragged of having easy access to ministers caused a furore in Westminster. Today the Conservatives will table a new House of Commons motion demanding more openness over lobbying.
John Redwood, the Conservative trade and industry spokesman, said that traditional British industries had suffered under Labour, while paid political advocates made more money than ever. "There is a massive expansion going on. As industry collapses, spin doctoring flourishes. This shows the unhealthy growth of the lobbyist culture under Tony Blair and his cronies," Mr Redwood said.
A register maintained by the Association of Professional Political Consultants, the lobbyists' professional body, shows that the volume of business has continued to increase.
In the second half of 1996 the association's 12 member companies had 468 clients on their books, including major corporations, charities and government bodies.
In the second half of 1998, after some takeovers and mergers, the same 12 companies had 633 clients - a 35 per cent increase.
Turnover among 10 lobbying firms that have filed recent accounts at Companies House rose by one-fifth from an average of pounds 1.9m in 1996 to pounds 2.3m in 1997. A comparison of the firms' staff numbers over the same period shows a rise of almost 27 per cent, from 183 to 232.
Among those who have left Labour since the general election is Cathy McGlynn, a former adviser to Jack Cunningham who now works for Bell Pottinger, the firm that represents the biotechnology company Monsanto.
Others include Jo Moore, a former senior media spokeswoman for Labour who now works for Westminster Strategy, and Karl Milner, a former researcher for Gordon Brown who now works for GJW.
Sources in the industry said the sector had grown rapidly since the election, but added that this was to be expected in a post-election period when a great deal of political change was afoot.
Charles Miller, the secretary of the association, said that demand for lobbying had been growing for a number of years, and an increase in turnover of 10 or 15 per cent per year would not be surprising.
However, Mr Miller added, lobbyists had not been given a particularly warm welcome by New Labour. Many felt that lobbyists were unnecessary and were a waste of their clients' money, he said, while a few believed they were "scum".
"There are very few backbenchers who believe that and even fewer ministers. But there are misconceptions about the work we do," he said.