A Conservative candidate standing in the Ealing Southall by-election recently donated £4,800 to Labour at a fundraising event.
Tony Lit headed the Asian radio station Sunrise at the time and was pictured with beaming smiles alongside former prime minister Tony Blair, despite criticising him in his campaign literature.
Labour has since seized upon this slip and released a photo of the generous donation cheque as well as the photo of Mr Blair with Mr Lit.
The businessman confirmed he had attended the fundraiser which he said was an event "for the Asian business community".
Mr Lit added: "But like many British Asians I feel the Labour government does not have the answers to the challenges that currently face the country."
A spokesman for the Conservatives said it would have been "odd" for Mr Lit to have not attended the event as Sunrise is such a major part of Asian business.
The event in London cost £4,800 per table and Mr Lit's father, Avtar, also bid an extra £4,000 for a weekend in Atlanta with two seats at a dinner with Hillary Clinton.
Before Mr Lit's presence at the Labour fundraiser had been confirmed, Mr Cameron had sung his praises.
He said ahead of the impending by-election: "I am delighted that we have selected Tony Lit. He is an outstanding candidate. Having worked in Southall for nearly a decade he really does understand and represent the needs of the local community."
Mr Lit was similarly happy at becoming the Tory candidate, saying that Mr Cameron's leadership showed the party "recognises people from all backgrounds".
The by-election will take place on Thursday July 19th at the same time as Mr Blair's former constituency Sedgefield elects a new MP.