Ed Miliband has been told Labour would be "tainted" if it accepted a donation from Tony Blair, given the former prime minister's business links with "questionable" undemocratic regimes.
On Tuesday it was reported that Blair, who is believed to be multi-millionaire, was considering making a substantial gift of cash to Labour ahead of the next general election.
But Conservative MP Henry Smith has written a mischievous letter to Miliband demanding he turn down any donation.
"I understand that you are desperate to find a source of funding that does not come with trade union loyalties attached, I feel it would be inappropriate for your party to accept any such donation from Mr Blair. Since stepping down as prime minister in 2007, Mr Blair has amassed a considerable personal fortune from a number of questionable sources," he said.
Among the former Labour leader's sins listed by Smith are his work for the dictatorship in Kazakhstan, which has been accused of "mass shooting of protestors", and for the government of Mongolia, where "police abuse of prisoners and corruption in the judicial system remain widespread".
Smith added: "I am sure you will also recall Mr Blair's recent public intervention, in which he described Egyptian military dictator Hosni Mubarak as 'immensely courageous and a force for good'. I would therefore respectfully suggest that the Labour Party should politely decline the offer of cash from Mr Blair, as any such donation would be irreversibly tainted."
It is not just Conservatives that are questioning the wisdom of Labour accepting money from Blair. Prominent left-wing columnist, and Labour Party member, Owen Jones asked on Twitter: "Tony Blair has been paid millions of pounds to work for Kazakhstan's dictator. Does Labour really want that dosh?"
Blair's fortune has been estimated to be in the region of £75m. As well as amassing substantial personal wealth, he has made charitable donations of £10m since 2007 - including £4m to the Royal British Legion.