A longtime friend and fundraiser of Barack Obama was accused of corruption yesterday at the start of a three-month trial that threatens to derail the Democratic front-runner's presidential campaign.

The prosecutor called Antoin “Tony” Rezko, a Syrian immigrant who became a property developer and political fixer in Chicago, “the man behind the curtain pulling the strings”. Mr Rezko, 52, is accused of using an accomplice on two state boards to demand kickbacks from companies that sought to do business with the state. He has pleaded not guilty.

Mr Rezko has known Mr Obama since 1990 and was one of the earliest fundraisers for his political career. The two also became entwined in a controversial property deal in 2005, a year after Mr Obama was elected to the US Senate, in which the Obamas bought a mock-Georgian home and Mr Rezko's wife bought the adjoining garden.

Prosecutors claim that Mr Rezko effectively controlled decisions by the Teachers Retirement System, which manages Illinois teachers' $30billion (£15 billion) pension fund, and the Illinois Health Facilities Planning Board, which must approve all building permits involving hospitals.

“Tony Rezko worked with an insider on two state organisations to corrupt those organisations,” Carrie Hamilton, the prosecutor, said.

Mr Obama is not accused of any wrongdoing in the case. Defence lawyers scoff at speculation that the Democratic front-runner will be called as a witness for Mr Rezko. But Mr Obama's name is likely to surface in the trial because some of the money allegedly paid as kickbacks ended up as a $10,000 contribution to his 2004 Senate campaign. Judge Amy St Eve has ruled that prosecutors can present evidence about the contribution as well as a $10,000 donation from Mr Rezko's associate Elie Maloof.

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