The Liberal Democrats said there appeared to have been "serious breaches of the law". The Prime Minister has been under mounting pressure since it emerged that more than £600,000 of donations to the party had been made via middlemen.
Property developer David Abrahams had tried to keep his contributions to the party's coffers quiet by using associates as conduits for the cash. He did not declare his own involvement to the Electoral Commission.
It emerged yesterday that Mr Brown's chief fundraiser, Jon Mendelsohn, had been aware of the situation - described by the premier himself as "unlawful". (Sky News)