Tim Farron is expected to say outgoing UKIP leader Nigel Farage and French far-right leader Marine Le Pen should not be allowed to "dictate our policy".
He is also expected to call for protection for EU workers in the UK.
Ms Le Pen has welcomed the Brexit vote, but Mr Farage has previously rejected ties with her party.
The Liberal Democrats are committed to continuing to campaign for the UK's EU membership.
Mr Farron will tell the centre-left think tank the IPPR that the 23 June referendum has left the UK "bitterly divided" and "we are in danger of letting malevolent forces hijack the result".
He will tell his audience in Manchester: "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.
"Britain is better than that."
France's National Front leader, Marine Le Pen, has said the UK's Brexit vote was "the most important moment since the fall of the Berlin Wall".
She and a number of other far-right leaders in Europe say they would like to hold their own referendums on EU membership.
Mr Farage has always rejected similarities between UKIP and the National Front, accusing the French party of "anti-Semitism and general prejudice".
Ms Le Pen, in turn, has accused Mr Farage of "aggression" against her party, for labelling it racist.
In his Manchester speech, Mr Farron will also say that there is "justified" anger among voters because "we have a political class, which I don't particularly like having to accept I'm a member of, which has abandoned people disastrously to their fate".
He will add: "We have a Treasury so cut off from reality that they urged people not to vote for Brexit because it might mean property prices would rise more slowly.
"As if people weren't struggling now to get a foot on the housing ladder."
He will argue that the Leave vote has created "new political boundaries which chop the old certainties of Tory and Labour into little pieces" and there is now a battle "between the forces of tolerant liberalism and intolerant, closed-minded nationalism".
A majority of voters backed leaving the EU in the vote in June - but, within days, 10,000 new members had applied to join the Liberal Democrats.
The party campaigned for a Remain vote and, following the result, Mr Farron said he would campaign to keep the UK in the EU at the next general election.
Mr Farron is also expected to back giving people from other EU member states living and working in the UK the right to stay, saying: "We can say to those from other countries who have committed their lives alongside us in the UK, 'We will stand by you, no matter what.'"
Politicians ranging from the pro-Leave Labour MP Gisela Stuart to the pro-Remain Scottish First Minister Nicola Sturgeon have called on the UK government to protect the rights of EU migrants.
Ministers have indicated that such a guarantee could be dependant on UK citizens living in other EU states being granted similar rights.
The EU referendum result could be hijacked by "forces of racism, intolerance and hate", the Liberal Democrat leader is to warn.