The Conservatives have received more than £100,000 in donations from companies and individuals connected to the lobbying industry since the party has been in government, an analysis of registered donations has revealed.
Only one of the companies listed as donors gave money to the Tories when they were in opposition and many of the payments were for a presence at party fundraising events.
Last night Labour accused the Tories of "using lobbyists as an extension of their fundraising activities".
The details emerged as the Electoral Commission announced it was investigating whether Tory fundraisers could have broken the law by soliciting donations which they believed to come from an overseas source.
The Commission was responding to a letter from the Labour former minister, Jack Straw, who drew up party funding laws and is now demanding a full formal investigation into allegations that the party was prepared to help donors get round rules requiring them to be registered to vote in the UK. "These reports raise serious questions as to how the Conservative Party is soliciting donations, potentially in contravention of the law," he wrote.
Among the lobbying companies listed as donating to the Conservatives was Hanover Communications, which gave £13,500 in 2010 and £8,000 last year. Hanover claims on its website that it helps clients "negotiate their way through the threat of regulation in the UK". The party also received £22,000 over two years from Bell Pottinger Communications, a sister company of Bell Pottinger Public affairs. Senior Bell Pottinger executives were secretly recorded during an investigation by the Bureau of Investigative Journalism and The Independent last year boasting about their influence in senior Tory circles. Last night Bell Pottinger said the donations had been for tables at party functions.
Other public affairs companies to donate include Sovereign Strategy, which gave £11,000 last September, and Huntsworth, which has given the party £24,000 in the past two years. Huntsworth is run by the Conservative peer, Lord Chaddlington, who, along with his wife, gave more that £12,000 to David Cameron's constituency party.
Labour also claimed that the Conservatives failed to include on its published list of invitees to Chequers three major donors who between them had given £2.4m. On Monday the party produced a list of six donors which it said was "complete to the best of our knowledge". But Labour said that Cabinet Office records showed that Lord Fink, the Tory Treasurer, Sir Christopher Gent, the former chairman of GlaxoSmithKline, and Paul Walsh, the chief executive of Diageo, also visited Chequers.