Cameron's office at first said that minister Liam Fox had the premier's "full confidence" despite the allegations about Adam Werritty, who was the best man at Fox's wedding but has no official government role.
But hours later Downing Street said Cameron wanted a preliminary report setting out the facts by Monday and was not prepared to wait until an internal Ministry of Defence inquiry reports back in a fortnight.
Fox -- who was visiting Libya on Saturday -- ordered the MoD inquiry on Friday into claims that Werrity posed as his advisor and had privileged access to him despite having no official government role or security clearance.
But the row intensified with new allegations in Saturday's newspapers that Werritty had brokered a meeting in Dubai in June between Fox and a company hoping to sell phone call encryption technology to the British military.
They discussed the possibility that British soldiers from Afghanistan use it to call home without being detected by the Taliban, or allo