UK Liberal Democrat leader Tim Farron yesterday described the EU referendum as the biggest political decision in “generations” and blasted the Prime Minister for trying to appease his right-wing colleagues.

Farron also used the Scottish LibDems conference speech in Edinburgh to criticise London Mayor Boris Johnson – a key Brexit figure – for “cynical manoeuvring” in backing the Out campaign.

He also attacked the SNP and said there is an “ugliness” to Scottish Nationalism that came out during the independence referendum.

Addressing delegates at the Scottish party's conference at the Assembly Rooms, he said: “The decision to remain or to leave is the biggest in generations for our country.

“And while the renegotiation was successful, it wasn’t central. It’s not central in the minds of most people. People across Scotland, across all of Britain will make up their mind on much bigger issues.

“Given that Europe is the world’s biggest market, will we be more prosperous if we remain or leave? Given that this is a dangerous and uncertain world, are we safer and more secure by staying alongside our closest friends and neighbours? Or turning our backs on them?”

The leader, who succeeded Nick Clegg, implied that the Prime Minister’s reform agenda for the EU is irrelevant:

“We have seen the Prime Minister return from his negotiations in Europe, eager to begin a charm offensive to persuade us of what we knew already: that we are better off in Europe than out of it.

“Boris Johnson’s cynical manoeuvring is not a threat to David Cameron who has already said he is going – it is a threat to a secure and prosperous future for the United Kingdom."

He said the reforms agreed between Cameron and other member states were about appealing to elements inside his own party.

“The renegotiation is all well and good, and we very much want reform. But 'Dave’s Deal' is about appealing to careerist Tory MPs, who were selected by Europhobic party members, to persuade them to vote to remain.

“And it’s not going too well. Gove, Villiers, Grayling, IDS, Whittingdale and Priti Patel. They’re only one lurid blazer away from John Redwood’s fantasy cabinet.”

Farron added: “The experience of generations is that Britain has enjoyed peace, security and prosperity inside the European Union.

“We must not throw that away in order to satisfy the narrow, nasty prejudices of those who would see us isolated and vainglorious in the world, harking back to Empire, or looking for some mythical fifty-first state status across the Atlantic.”

He also took aim at the SNP: “There is sadly an ugliness to some elements of Scottish Nationalism which many of us in the rest of the United Kingdom simply don’t see. We saw it during the referendum – with SNP candidates and campaigners alike seemingly determined that no other views than their own should receive a hearing.

“Ordinary folk, getting involved in politics, sticking up for their communities, were made to feel that they have no place in Scotland unless they supported Sturgeon and her crew.”