Image caption Allen Stanford denies the allegations against him

A US federal judge has ruled that Texan billionaire Allen Stanford is unfit to stand trial at present over accusations he led a $7bn (£4.5bn) fraud scheme.

Mr Stanford is facing trial over allegations that he ran a pyramid scheme based in Antigua which defrauded investors.

He has pleaded not guilty to fraud, conspiracy and obstruction.

District Judge David Hittner ruled that Mr Stanford did not have the present mental capacity to assist his lawyers.

But he ordered Mr Stanford to undergo treatment at a US prison hospital for an addiction to an anti-anxiety medication, and also receive additional psychiatric testing.

"The court finds Stanford is incompetent to stand trial at this time based on his apparent impaired ability to rationally assist his attorneys in preparing his defence," Judge Hittner wrote in his ruling in Houston, Texas.

"The court's finding that Stanford is incompetent, however, does not alter the court's finding that Stanford is a flight risk and that no combination of conditions of pretrial release can reasonably assure his appearance at trial," he added.

The charges against Mr Stanford capped a rapid fall from grace for a man who had shot to prominence in the UK and the Caribbean for his lavish sponsorship of cricket.

'Too good to be true'

Mr Stanford, 60, is accused of running a scheme which persuaded investors to buy certificates of deposit from Stanford International Bank, located in Antigua.

Prosecutors have said they "promised returns that were too good to be true".

Mr Stanford has been in custody since June 2009, when he surrendered to the US authorities after a warrant was issued for his arrest.

His trial had been expected to start this week, but the judge said he would set a new trial date once the results of the detox and further testing were in.

Psychiatrists testified at a prior hearing that Mr Stanford was suffering bouts of delirium linked to his addiction and also said he was incompetent to stand trial due to a brain injury he suffered as a result of a fight with a prison inmate in 2009.

Mr Stanford invested heavily in West Indies cricket and built his own cricket ground in Antigua, where Stanford Financial Services was based.

In 2008 he bankrolled a high-profile $20m cricket match between England and a Stanford All-Stars team on the island.