PRO-EU SCOTLAND will be the key factor to winning the battle to keep Britain in the European Union, says Norman Lamb, the former Coalition Minister, who is hoping to succeed Nick Clegg as leader of the beleaguered Liberal Democrats.

The MP for North Norfolk, one of only eight Lib Dems out of 57 to survive the General Election drubbing, believes the forthcoming referendum will help revive the party, which has been "running on empty for too long" and needs once again to become the "intellectual powerhouse" of British politics.

Mr Lamb, in Scotland this weekend for a series of hustings with his rival for the Lib Dem crown, Tim Farron, noted in an exclusive interview with The Herald how, in a close-run referendum, Scottish voters would be the difference between staying in or leaving the EU.

"Opinion in Scotland is going to be pretty decisive in terms of the overall outcome on this. I get the impression there is a stronger pro-European sentiment in Scotland than there is in some parts of England. So that will be decisive."

The 57-year-old politician branded Nicola Sturgeon's proposal for a Scottish veto on the referendum result dangerous, noting: "If we stayed in the EU just because of a vote in Scotland, there would be massive resentment from other parts of the UK, which would be a very difficult political situation to deal with. So we have to vote as a United Kingdom but votes in Scotland will be decisive."

Mr Lamb stressed, while his party was, unlike the Conservatives or Labour, united in wanting Britain to stay in the EU, this did not mean it had to lose its critical faculties, explaining that arguing for sensible reforms to make the bloc more accountable meant "you get more of a hearing as a pro-European party than you do if you try and claim that everything is perfect".

He claimed the referendum could be the catalyst to reviving Lib Dem fortunes and that he wanted the party's mindset to be "we must be ready for opportunities that come along and there will be opportunities in this parliament; it's going to be dominated by the European referendum...The first referendum fractured the Labour Party and led to the creation of the SDP. It's perfectly possible the Tory Party could tear itself apart over this".

The East Anglian MP said the fearmongering in the election about a Lab-SNP alliance was "ruthlessly exploited" by the Tories and played "massively" on the doorstep in England.

"Elections are won and lost on emotion...In 1997, it was hope; in 2015, it was very much fear...It was a really powerful emotion, particularly in the last week with people saying - we want to have you as our MP but we are really scared. What they were scared of was Ed Miliband, who no one could see as a prime minister, being dictated to by the SNP."

While Mr Lamb accepted his party was at a low ebb - it now has one UK MEP, one Scottish MP and one Welsh MP - he made clear to be a Liberal Democrat was to be an eternal optimist.

The backbencher argued that people now behaved as consumers with regards to politics, which meant views could change quickly.

"In commerce, household names are here today, gone tomorrow; same thing happens in politics with the SNP growing very rapidly because they connected with people...In very many respects this is a liberal age; there are many people who have liberal instincts and values. If we can connect with those people, we could become successful much more quickly than people imagine."

The would-be party leader does not regard himself as "tainted" by being part of the Coalition, making clear as the Minister for Care and Support he enhanced his reputation as he sought to improve the care of those who suffered from mental health problems.

When it was pointed out how Mr Farron, who represents Westmorland and Lonsdale in Cumbria, had conspicuously stayed out of the Coalition government, Mr Lamb smiled and said: "Yeah. I'll just deal with my situation," stressing: "Even my non-comment is off the record."

When it was stressed that everything was on the record, he replied: "Well, okay, let me put it this way. The party voted democratically to go into the Coalition. I had no idea whether Tim was ever invited or asked to be a Minister. I absolutely felt that it was responsibility to step up to the plate and take my responsibility as part of that.

"But, ultimately, it's what you do in government that matters. Certainly, so far as any judgement I have seen from anywhere, I came out with my reputation significantly enhanced as a result of the work I did as a campaigning Minister fighting for equality for those suffering from mental ill health."

He added: "If people just choose to condemn me because I participated in government, then fine. But people need to know who I am and what I'm about. Once they know that, they realise this is a mission I'm on."

While Mr Lamb is regarded as the underdog, he believes that, because there were now 17,000 new Lib Dem members, the race for the leadership is "wide open". He and Mr Farron will know their fate on July 16.