Nick Clegg has said Syria's president Bashar al-Assad is as "irrelevant" to the country's future as Colonel Gaddafi is to Libya.

In a speech on Monday afternoon, the deputy prime minister said the momentum of change in the Arab world, and the pace of events overnight in Libya was "breathtaking".

But he echoed the prime minister's cautious tone on Libya, warning "we should learn the lessons from Iraq" and that the rebels' advance into Tripoli was merely the beginning.

"Today’s scenes should give heart to all of those struggling for their freedom ... [But] Gaddafi’s departure will not be the end. It will be the beginning and we should not underestimate the challenges ahead."

He also made it clear the UK stood "shoulder-to-shoulder" with protesters in all Arab countries: "We believe in the same things these activists are fighting for: freedom, self-determination, human rights, the chance for people who work hard to succeed."

However Clegg said the movement for freedom across the Arab world was "here to stay": "The advances made by the Free Libya Forces in Tripoli would have been unthinkable just a few months ago. Unimaginable, even, for the generations of young Libyans who have never known a world without Gaddafi. Now, that world is within their reach.

"The momentum for change is breathtaking and, for the cynics who said change wasn’t possible, who had written off the Libyan uprising, written off the Arab Spring, clearly, they were wrong."