British Deputy Prime Minister Nick Clegg on Tuesday said it is "only a matter of time" before Colonel Muammar Gaddafi is defeated.
Speaking following a meeting of the National Security Council on Tuesday, Clegg said the reappearance of Saif al-Islam was "not the sign of some great comeback" for the regime.
Saif al-Islam has denied his arrest and insisted his father was safe and well in Tripoli.
Clegg said Gaddafi and the remaining pro-Gaddafi forces are now cornered. They are making their last stand and it's only a matter of time before they are finally defeated.
Prime Minister David Cameron has resumed his holiday in Cornwall after he cut it short on Monday to chair a Libya meeting.
On Monday, Cameron spoke outside Downing Street No. 10 and stressed the situation in Libya was very fluid and that there was no room for complacency.
The prime minister also said the transition to a free and democratic Libya should be a "Libyan-led and Libyan-owned process."
He said "Our task now is to do all we can to support the will of the Libyan people which is for an effective transition to a free, democratic and inclusive Libya."
Cameron said the British government would establish a "diplomatic presence" in Tripoli as soon as it was safe to do so and said Britain could be proud of its role in helping the uprising against Gaddafi.
The wider NATO mission in Libya to protect civilians will continue as long as it is needed and Cameron said the focus was now on the urgent work that needs to be done on providing medical and humanitarian aid, diplomatic support, and work through the UN Security Council.