The "malevolent forces" of former Ukip leader Nigel Farage and National Front chief Marie Le Pen are attempting to hijack the Brexit vote in a bid to promote their "intolerant" politics, Tim Farron will claim. The Liberal Democrat leader is expected to issue the warning as he speaks at the IPPR think tank in Manchester today (30 July).

"Plenty of my mates voted Leave and I can tell you that the majority of those who did vote Leave are utterly appalled that Farage, Le Pen and their ilk now seek to claim the result as a victory for their hateful brand of intolerance, racism and insularity," he will say.

"Britain is better than that." Farron, who campaigned for a Remain vote at the EU referendum, is also expected to criticise the UK's political class-at-large for living the country "bitterly divided".

"Between parents and children, families, neighbours. Between the nations of our own union, who have worked and fought together for centuries," he will add.

"Between us and our continental neighbours. And now the biggest danger of them all. That because of those divisions, we are in danger of letting malevolent forces hijack the result."

Farron will also join Labour's Gisela Stuart, who chaired the Vote Leave campaign, in calling for protections of EU citizens in the UK "to use what power we can muster, to make sure that those who have committed their lives and families to this country will be protected," the Liberal Democrat leader will declare.

"That no knee-jerk populism will be allowed to threaten them or uproot them. And I ask now all the many candidates for high positions in Westminster to join me in this undertaking."

The speech will come as pressure mounts on Prime Minister Theresa May to spell out what she meant by "Brexit means Brexit". The Conservative premier has so far set up a Department for Exiting the EU, which is headed up by Leave campaigner and former Europe minister David Davis.

But the Tory government has far failed to provide a timetable for triggering Article 50 of the Lisbon Treaty, the official mechanism to split from the EU. Iain Duncan Smith, the former Conservative leader, has suggested it could be triggered in early 2017.