John Major urges Theresa May to defy ultra-Brexiteers, change course and give MPs free vote on Brexit deal

Describing quitting the EU as a “mistake of destiny,” the ex-Labour leader will say: “The British people should be given a final say on whatever deal is negotiated. If they are allowed that say, then Brexit can be averted.”

Analysis by Kirsty Hughes: Phoney war is over, now the stress is really on May’s government

The high-profile interventions of her predecessors came as the Prime Minister responded to a draft withdrawal agreement from the European Commission whose "backstop" plan would effectively keep Northern Ireland in the customs union; unless the UK was able to set out an alternative solution to avoid the imposition of a hard border.

Making clear her bottom line was defending the “constitutional integrity of the United Kingdom,” she told MPs the Brussels plan would create a customs border down the Irish Sea, which would undermine the UK’s common market.

“No UK Prime Minster could ever agree to it,” she declared.

Faced with an accusation from the SNP’s Ian Blackford that her government was acting like “Big Brother” on the EU Withdrawal Bill by undermining the devolved settlement, Mrs May insisted the Scottish Government’s planned Continuity Bill was “unnecessary” and urged Nicola Sturgeon and her colleagues to re-engage in talks.

Another Joint Ministerial Committee is due next Thursday before a PM-FM showdown later in March.

READ MORE: Boris Johnson urged to go over his "reckless" comments on Northern Irish border issue

Just two days before Mrs May is due to give her latest keynote speech on Brexit, Sir John, whose own premiership was dogged by quarrels over Europe, launched his broadside in a speech in London, warning of a "terrible backlash" from the public if EU withdrawal left the UK poorer and weaker; as forecasts suggested.

Claiming the UK Government's current negotiating position was unrealistic, he urged the PM to drop her red lines and be prepared to "change course" and seek a Norway-style solution, which would involve accepting single market rules and paying for access to EU markets.

Sir John argued that it was "not credible" to expect to leave the single market, customs union and European Court of Justice while at the same time seeking a-la-carte access to European markets.

He pointed out how the Conservative Party over many years had understood the concerns of business but not, it seemed, over Brexit.

“Across the United Kingdom businesses are expressing their wish to stay in the single market and customs union but no say the Government’s red lines…This is not only grand folly, it’s also bad politics,” declared the former PM.

Analysis by Kirsty Hughes: Phoney war is over, now the stress is really on May’s government

Sir John said Mrs May should make clear that the "meaningful vote" promised to MPs on the final Brexit deal should be a free vote and should have the options of accepting or rejecting the outcome, sending negotiators back to seek improvements or calling a second referendum.

“Let Parliament decide or put the issue back to the British people," he insisted.

Stephen Gethins for the SNP welcomed the former PM’s remarks, saying he was “right to warn of the catastrophic consequences that Brexit will have on the UK” and that his words should serve as a wake-up call to Mrs May.

But leading pro-Brexit Tory Jacob Rees-Mogg said Sir John’s speech was “riddled with errors and humbug” and urged him to go away, do his homework and try then to make a statesman-like speech.

Meanwhile, Mrs May has U-turned on EU citizens’ rights during the transition, accepting new EU migrants who come to Britain during the two-year period will have the right to settle permanently in the UK.

The concession was slipped out in a Brexit policy paper from the Home Office and says new EU migrants arriving after March 2019 will be given a five-year temporary residence permit; not the two-year one previously proposed.