George Michael and Andrew Ridgeley rock out (Express Newspapers/Getty)

The boss of an American HIV AIDS charity has revealed George Michael donated hundreds of thousands of dollars to keep the organisation going.

The generous donations remained a secret during Michael’s life – insisting on sending the money anonymously so as to not draw attention to himself.

Project Angel Food – a charity based in Los Angeles – was founded by volunteers in 1989 to help those suffering from malnutrition and HIV.

Richard Ayoub, executive director of Project Angel Food, revealed the star’s connection to the trust and told The Mirror: “We can’t thank him enough.

“He was so supportive and is the single largest donor in our history. He sent a $25k donation to us religiously every year to the tune of more than half a million dollars.

“His passion and love and support was felt here every single year.”

The charity boss said the star insisted on sending the cheques privately to avoid “fanfare”.

He even auctioned his Mercedes car and donated the proceeds to the charity.

In 1994 the charity saw a significant increase in demand for their services.

Men who had been diagnosed with HIV were turning to the charity as they struggled to keep their spirits up and look after themselves.

When popstar Michael, who wasn’t openly gay in 1994, heard about the charity’s work he insisted on helping.

One morning, as Project Angel Food struggled to cover their bills, a letter appeared at their offices.

It contained a note thanking them for their good work and a cheque for $25,000, signed ‘George Michael’.

He went on to donate $25,000 every single year until his death, becoming the charity’s biggest ever donor.

The charity held a special gala to celebrate the singer’s life and generosity in memory of his commitment to their project.

RELATED: George Michael did NOT want to be gay, claims friend

Adam Lambert, who has been on tour as Queen in Freddie Mercury’s spot, paid an emotional tribute at the event.

The former American Idol and Queen singer has said the late Wham! frontman was one of his musical role models.

Watch him take to the stage to perform Faith below

George Michael was named as a recipient of the Elizabeth Taylor Humanitarian Award at the 2017 gala.