SIR John Major has warned that the “agonies of Brexit” could break up Britain and lead to an independent Scotland.

Giving the inaugural lecture at the John Smith Centre for Public Service at Glasgow University, the former Prime Minister warned Tory right-wingers that they should not allow their obsession with leaving the European Union to blind them to the potential disappearance of a more historic union: the United Kingdom.

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In his speech, Sir John claimed that in the era of social media, populism and so-called fake news a fundamental truth had been lost: that the vast majority of politicians were diligent public representatives, who fought and voted for what their consciences believed and their philosophy dictated.

He recalled his political relationship with the late John Smith, saying: “John was a rare talent; the sort of tenacious politician that our country could ill afford to lose. If the fates had allowed, he would have been a prime minister of distinction.”

The former Conservative leader insisted he was proud to honour the legacy of a former Labour leader.

“John and I were political opponents but never personal ones. I admired his ability and conviction even when I disagreed with him.

“At PMQs, adrenaline propelled both of us to remarks that, perhaps, were best not made but, when the ritual was over, we withdrew occasionally to my room in the Commons to enjoy a drink; or two.”

Commenting on today’s political scene, Sir John bemoaned how Britain’s two main parties were being “manipulated by fringe opinion”.

“In Parliament, the European Research Group has become a party within a party with its own whips, its own funding and its own priorities. Some of its more extreme members have little or no affinity to moderate, pragmatic and tolerant Conservatism.

“The ERG does not represent a majority view but – with a minority Government as now – can determine policy simply by being intransigent; which is precisely what it is doing.

Some, who can fairly be called zealots, seem incapable of looking beyond the one issue of Europe. It’s not just that it dominates their thinking; it seems to obsess them,” he declared.

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Labour, argued the former PM, had a different dilemma but faced a similar outcome.

“It has enjoyed a vast growth in membership that has captured many constituency organisations, their national conference, important party positions and has left control of policy at the mercy of a passionate, active, far-Left base rather than the centre-Left.

“Yesterday, seven moderate MPs left the Labour Party. I admire their courage and their conviction. But I hope they have not cut themselves adrift forever. Labour needs moderate MPs and the country needs a moderate Labour Party,” he insisted.

Sir John said he feared the UK was about to move from a position of power and influence around the world to one of relative isolation and weakness.

Turning to constitutional matters, he said it was painful to come to terms with the possibility that, within his lifetime, her could see the break-up of the UK.

“I hope I am wrong but the agonies of Brexit have the capacity to do just that,” he warned.

“Some argue that a break-up won’t happen because economic logic is against it. But sentiment and emotion is a potent mix: economic logic was against Brexit, yet look where we are now.

“I am not suggesting it is pre-determined that Scotland and Northern Ireland will leave the UK, it is not. But I am suggesting that leaving the EU will make an independent Scotland and united Ireland more likely than if we remained in the EU.”

He went on: “In 2015, Scotland voted to stay in the UK and in Europe. Yet English and Welsh votes are now taking Scotland out of Europe against their will. Scotland cannot apply to re-join unless they gain independence. The incentive to try again is clear.

“As for Northern Ireland, Sinn Fein are already calling for a new Border Poll on a united Ireland. This call will become more compelling if there is a ‘hard’ border, with all the risks of a return to violence.

“I don’t believe a Border Poll would succeed in the near future but, within a few years, who can be sure?”

And turning to who some describe as “English Nationalists” within the Tory Party, Sir John noted: “It is astonishing to me that English Unionists are so avid to leave the European Union, that they are willing to put at risk our far more historic union with Scotland and Northern Ireland.”

Pointing to next week’s key Commons vote on Brexit, he urged MPs to vote for an outcome that best protected the future welfare and prosperity of Britain “without fear or favour and without defence to party allegiance”.