Mosley will have to go – Stewart
Mosley is under pressure to quit after a newspaper claimed he took part in a "Nazi-style orgy". He denies his actions had any Nazi connotations.
Stewart told the BBC that the big companies which back F1 want Mosley out on both commercial and moral grounds.
"He's gone beyond anything they would tolerate," Stewart told Radio 5 Live.
Stewart, who has clashed with Mosley over many issues in the past, said the sport's big backers had met at the Spanish Grand Prix to discuss the issue.
He said Mosley's behavior would have contravened the companies' "corporate moral guidelines" and that motor clubs around the world, which also come under the auspices of the FIA, would not approve either.
"Therefore it's very difficult to see how he could stay under these circumstances," added Stewart.
"I think it's going to be very difficult commercially for the companies involved in Formula One to carry that and the motor clubs to carry it. I think that's quite serious." BBC Sports