Fox has been under pressure for days over his former flatmate Adam Werritty, who posed as his advisor and accompanied him on 18 overseas trips to countries including Sri Lanka and Dubai, despite having no governmental official role.
As Fox, 50, caught a train from London to Paris where he was due to hold talks with his French counterpart, he said he had no intention of standing down amid the controversy over the 34-year-old Werritty.
"I shall carry on doing the job that I am meant to do, the job that I am paid for," the defence secretary told reporters.
But in a new twist, Fox was forced to deny that his ruling Conservative party had lied about a break-in at his London home last year, when it said he had been alone in the house at the time.
The Sun newspaper reported that a "younger man" had been staying the night at the apartment when thieves broke in and took a laptop, a mobile phone and the keys to Fox's car.
In a statement, Fox said he was "appalled at being portrayed