Labour slumped to third place in Scottish politics behind the Conservatives because the party "gave up the middle ground", former prime minister Tony Blair has claimed.

Mr Blair, Labour's longest-serving prime minister, insisted it is a "myth" that Scotland is a left-wing country, saying the reality has "always been much more complicated than that".

He said Brexit gives the party the opportunity to win again north of the border - if Scottish Labour commits itself to opposing withdrawal.

Scottish Conservative support for the UK leaving the European Union is where Ruth Davidson's party is most vulnerable, Mr Blair argued.

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He told Holyrood magazine: "I think what the Brexit thing really does offer us is a huge opportunity because, by the way, the vulnerability of Ruth Davidson's Conservatives is that they are tied to Theresa May.

"That is a vulnerability, but it's only a vulnerability you can exploit if you're prepared to say, 'We'd stop the thing'. So, you've literally got those votes just lying on the table waiting to be taken, you just need to say it."

The ex-PM was speaking after a number of Labour MPs quit the party for the newly formed Independent Group at Westminster, citing party leader Jeremy Corbyn's failure to oppose Brexit as one reason for their move.

Mr Blair was UK Labour leader when the party lost power at Holyrood to the SNP in 2007. Since then it has fallen behind the Tories to become the third party in the Scottish Parliament.

Scottish Conservative support for the UK leaving the European Union is where Ruth Davidson's party is most vulnerable, Mr Blair argued.

He argued that by opposing Brexit, and by fighting the SNP on its record on public services, Labour could win again.

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He said: "What is the obvious thing for the Labour Party to do in Scotland right now? The absolute obvious thing, it's just sitting there, like a great big prize. You become the party that believes in the union, but with max devolution within it. You are pro-Europe, so you fight Brexit.

"Absolutely, you don't go along with it. And you're the party of economic and social reform where, frankly, around public services and other things, the SNP are vulnerable. If you put those three things together, then you could win.

"The question the Labour Party should ask itself in Scotland is how do you get beaten by the Tories? Why is that happening? It's happening because it's the politics that Ruth Davidson represents. That's why it's happening. You gave up the middle ground."

Responding to the claims made by the former PM, Nicola Sturgeon tweeted: "A case of serious misdiagnosis here..." 

A Scottish Labour spokesman said: "Our common sense policies will end the cruel austerity the Tories have inflicted on our communities, where the only growth has been to levels of poverty, homelessness, inequality and foodbanks.

"Ruth Davidson's Tories brought us the bedroom tax, the two-child cap and rape clause, and she has supported May's Brexit shambles at every turn. They oppose everything that we stand for.

"We will build an economy that works for everyone, where the wealthiest pay more so we can invest in jobs, schools and hospitals, end low pay and the exploitation of workers, and put people before profit by bringing public services like buses and trains into public ownership.

"The Tories not only can't do any of this, they don't want to."

Jackson Carlaw, Scottish Conservative interim leader while Ms Davidson is on maternity leave, said: "Tony Blair is absolutely right.

"Under Ruth, the Scottish Conservatives are in the mainstream of Scottish politics - opposing Nicola Sturgeon's plan to take us back to a second (independence) referendum so we can all focus on the things that matter, like our NHS and education.

"It's why thousands of former Labour voters in Scotland now back Ruth and her team to take on the SNP."

An SNP spokesman said: "It is the SNP who occupy the centre ground of Scottish politics and mainstream Scottish opinion, while the Tories and Labour move to the extremes and the Lib Dems slide into irrelevance.

"That is only likely to continue as both Labour and the Tories split, while the SNP get on with the job of protecting vital public services and standing up for Scotland."

Scottish Labour leader Richard Leonard tweeted: "This is completely wrong. The Tories are far from the centre ground of politics.

"What people want is an end to austerity and the rip-off of privatisation, and for more power to be in the hands of the many, not the few."