Nick Clegg has pledged that Britain will not be intimidated by jihadist extremists, saying that the country is united in the fight against Islamic State.

Making the keynote speech at his party’s conference, the Liberal Democrat leader described Isil as a brutal organisation that was perverting Islam.

He said: “We have to defeat their barbarity to help protect the millions of people who now live under the threat and fear of these merciless killers.”

He told the audience in Glasgow that all Isil had done “is unite the people of Britain – Muslim and non-Muslim, people of all faiths and none – around a single aim.

“We and our allies – including in the Middle East – are going to find you, we are going to destroy your bases, we will cut off your supplies, isolate you from your support – and for the sake of peace, democracy and the freedom of all those you terrorise, we are not going to stop until it’s done.

Mr Clegg said his party’s condolences went out to the families of British aid workers Alan Henning and David Haines, who were murdered by Isil, calling their killers “cowards”.

Referring to the Scottish referendum, he said the campaign had forced Britons “to hold up a mirror and think about who we are,” noting that “these Isles of ours are among the most diverse and inclusive in the world.

“You can be British as well as Scottish, English, Northern Irish, Welsh…ish. At the same time you can be black, white, Asian, Indian, African, European, mixed, not-mixed. You can be gay, straight, bi-sexual, transgender. Christian, Muslim, Jewish, Hindu, Sikh, atheist”.