Ed Miliband has had eight formal meetings or dinner with Len McCluskey, the Unite general secretary, since he was elected Labour leader in September 2010, the party said on Friday.
McCluskey and fellow union leaders dominate a list published by Labour of all 43 meetings and dinners that Miliband has had with trade union bosses and individuals who have given large sums to the party. Miliband promised to release the list after David Cameron published the names of major donors to the Conservative party who have been entertained at No 10 or Chequers after the cash-for-access row erupted.
Labour said that their list went further than Cameron's. While the prime minister only named those giving his party more than £50,000, of whom 12 were entertained at Downing Street and five at Chequers, Miliband listed his meetings with anyone giving Labour more than £7,500.
Lady Warsi said the fact that McCluskey, whose union has given Labour £5m since Miliband became leader, appeared on the list more than anyone else showed that Labour "is the political wing of 'Red' Len McCluskey's Unite trade union".
But McCluskey has not been entertained at Miliband's home and only one of his meetings involved a dinner. That was a meal in the Commons in April 2011 attended by five other union leaders.
Only three donors have had dinner at Miliband's north London home. They are Ken Livingstone, Labour's candidate for London mayor; Andrew Rosenfeld, the property tycoon who has joined the party as a fundraiser; and Nigel Doughty, the late Nottingham Forest owner who gave Labour more than £3.5m over the last seven years.
Doughty was the only person on the list entertained by Miliband twice. He had dinner at the Milibands' in November 2011, and breakfast at their home in March 2011.
Many of the names on the list are union leaders, such as the GMB general secretary Paul Kenny, who has met Miliband six times, and Dave Prentis, the Unison general secretary, who has met him five times. The business figures Miliband has met include property tycoon Kevin McGrath, ex-chairman of Green & Black chocolate, Henry Tinsley from Betterworld and Canary Wharf developer Sir George Iacobescu.
Cameron announced on Friday that the Conservative party's internal inquiry into cash-for-access, which is being chaired by the Tory lawyer Lord Gold, will also include Lord MacGregor, the former cabinet minster, and Lady Browning, the former minister.
In a separate development Ed Staite, a former Conservative official who now works as a communications consultant, wrote a post on his blog revealing that he had been the subject of an undercover operation by the Sunday Times journalists following up their cash-for-access scoop.
He published an email he had received from a Sunday Times journalist saying that a meeting he had have with people posing as wealth fund executives in February had actually been a meeting with undercover reporters.
The email said the Sunday Times was preparing a story saying that he had told the reporters "they could influence the next Conservative manifesto by paying for a policy group 'in an area that fits your agenda'." The email also said Staite had told them that policy making groups could be bankrolled either with cash sponsorship or by paying for a secretariat.
On his blog, Staite said the email suggested the Sunday Times were going to misrepresent what he said and that this was "entrapment of the worst kind".
He explained: "I was asked a number of times whether I could secure a meeting with George Osborne if they paid money to the Conservative Party. I flatly, and firmly, said no.
"This led me to outline how the best way to positively engage in the political process is to sponsor policy making. This is completely transparent and a positive way to help political parties or think-tanks to renew and help meet the demands of modern Britain."
