Owen Bennett-Jones, in Islamabad: "It is expected Benazir Bhutto will also be charged by the Swiss."

The documents, which have been examined by the BBC, include a formal charge of money laundering and an indictment by the Swiss authorities against Mr Zardari.

A Swiss magistrate says he has evidence that Asif Zardari received commissions from two Geneva-based companies which had contracts with Pakistan's Government.

Mr Zadari is also charged with trying to launder the money - an offence under Swiss law.

The Pakistani Government says it will serve the papers on Mr Zardari, who is currently in prison on separate charges relating to the murder of Benazir Bhutto's brother.

Diamond necklace

The documents also allege that money appeared to be accessible to Benazir Bhutto and that in August 1997 she used some of it to purchase a diamond necklace for over $175,000.

A spokesman for Benazir Bhutto denies that she ever made the purchase, and her opposition Pakistan People's Party claims that the Swiss authorities have been misled by false evidence provided by Islamabad.

So far, the Swiss have only charged Asif Zardari, but senior Pakistani officials say they expect that Benazir Bhutto will also be charged in two or three weeks' time.

But Pakistan officials say the documents mark considerable progress in their efforts to prove corruption allegations against Miss Bhutto and her husband.