Tony Blair has defended his treatment of Muammar Gaddafi while in office, saying it was "great" the Libyan leader had stopped sponsoring terrorism.
The former PM shook hands with Colonel Gaddafi after talks in Libya in 2004 and re-opened diplomatic links.
On Wednesday a group of countries including the UK, US and France called on the Libyan leader to step down.
Mr Blair said he agreed that change had to be "forced" but added that he had not been "wrong" to restore relations.
UK Prime Minister David Cameron is to travel to Paris later for a meeting with French President Nicholas Sarkozy on the Libyan crisis, which has seen widespread fighting between pro and anti-Gaddafi forces.
In 2004, Mr Blair met Col Gaddafi in the desert near Tripoli for talks following the Libyan leader's renunciation of weapons of mass destruction.
At the same time it was announced that Anglo-Dutch oil firm Shell had signed a deal worth up to £550m for gas exploration rights off the Libyan coast.
But the meeting came after years of strained relations following the 1988 Lockerbie bombing and murder of WPC Yvonne Fletcher outside the Libyan embassy in London in 1984.
Mr Cameron has criticised Mr Blair's government for conducting "dodgy deals in the desert".
However, Mr Blair told the BBC: "I don't think we were wrong to make changes in our attitude to Libya when they changed their attitude to us.
"So I think the fact they gave up their chemical and nuclear programme, the fact they stopped sponsoring terrorism and cooperate in the fight against it was great."
Mr Blair, who is now Middle East envoy for "the Quartet", made up of the United Nations, the European Union, Russia and the United States, also said: "But what didn't happen - and people hoped it would but it didn't - was that the external changes in Libyan policy were matched by internal changes.
"And now what you've got over these past few weeks has been totally unacceptable and that's why I think there's no option but to take action and force change there."
Mr Blair's predecessor as Prime Minister, Sir John Major, has also defended the meeting with Col Gaddafi.
He said the abandonment of weapons of mass destruction had been "a very significant prize" for the UK.