Two former prime ministers have issued a plea to MPs not to “wreck” the Northern Ireland peace process and risk the break-up of the United Kingdom by approving Boris Johnson’s Brexit deal.

Tony Blair and Sir John Major said that the withdrawal agreement – due to be put to a vote in the Commons on Saturday – represents “a reckless gamble with people’s lives and a fragile peace”.

In a video message to Saturday’s Together for the Final Say rally in London, the two ex-premiers will restate their full support for the demand of hundreds of thousands of marchers for a referendum on any deal.

Mr Blair, who was PM when the Good Friday Agreement was signed in 1998, said it was “a shame and an outrage” that peace in Northern Ireland was being treated as “some disposable inconvenience to be bartered away in exchange for satisfying the obsession of the Brexiteers with wrenching our country out of Europe”.

And Sir John, who began the talks process which led to the historic agreement, said he found it “extraordinary” that the Conservative and Unionist Party which he once led was now ready to take a course which “may in the future break apart the United Kingdom”.

People's Vote march – demanding vote on final Brexit deal Show all 30 1 /30 People's Vote march – demanding vote on final Brexit deal People's Vote march – demanding vote on final Brexit deal Mandatory Credit: Photo by Guy Bell/REX (9725259aq) Marching down Whitehall - People's March for a People's Vote on the final Brexit deal. Timed to coincide with the second anniversary of the 2016 referendum it is organised by anti Brexit, pro EU campaigners. People's March for a People's Vote, London, UK - 23 Jun 2018 Guy Bell/REX Rex People's Vote march – demanding vote on final Brexit deal Demonstrators carry banners and flags as they participate in the People's March demanding a People's Vote on the final Brexit deal, in central London on June 23, 2018, the second anniversary of the 2016 referendum. Tens of thousands of people demonstrated in London on Saturday calling for a second vote on Britain's departure from the European Union. / AFP PHOTO / Niklas HALLE'NNIKLAS HALLE'N/AFP/Getty Images NIKLAS HALLE'N AFP/Getty Images People's Vote march – demanding vote on final Brexit deal A young protestor shouts as she takes part in the People's Vote demonstration against Brexit Getty Images People's Vote march – demanding vote on final Brexit deal A woman holds a placard as she joins EU supporters, calling on the government to give Britons a vote on the final Brexit deal, participating in the 'People's Vote' march in central London, Britain June 23, 2018. REUTERS/Henry Nicholls HENRY NICHOLLS Reuters People's Vote march – demanding vote on final Brexit deal epa06833888 Pro-EU demonstrators take part in a People's March anti-Brexit rally in Parliament Square in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal A protester's pro-EU t-shirt EPA People's Vote march – demanding vote on final Brexit deal epa06833892 A pro-EU demonstrator waves a European Flag during a People's March anti-Brexit rally in Parliament Square in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal Demonstrators carry banners and flags as they participate in the People's March demanding a People's Vote on the final Brexit deal, in central London on June 23, 2018, the second anniversary of the 2016 referendum. Tens of thousands of people demonstrated in London on Saturday calling for a second vote on Britain's departure from the European Union. / AFP PHOTO / Niklas HALLE'NNIKLAS HALLE'N/AFP/Getty Images NIKLAS HALLE'N AFP/Getty Images People's Vote march – demanding vote on final Brexit deal epa06833960 Tens of thousands of people march through London during a People's March anti-Brexit demonstration in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal Leader of the Liberal Democrats, Vince Cable speaks during the People's March demanding a People's Vote on the final Brexit deal, in central London on June 23, 2018, the second anniversary of the 2016 referendum. Tens of thousands of people demonstrated in London on Saturday calling for a second vote on Britain's departure from the European Union. / AFP PHOTO / Niklas HALLE'NNIKLAS HALLE'N/AFP/Getty Images NIKLAS HALLE'N AFP/Getty People's Vote march – demanding vote on final Brexit deal epa06833964 A young pro-EU demonstrator takes part in a People's March anti-Brexit rally in Parliament Square in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal Gina Miller and Caroline Lucas EPA People's Vote march – demanding vote on final Brexit deal epa06834044 Tens of thousands of people march through London during a People's March anti-Brexit demonstration, in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal epa06833264 Thousands of people march through London during a People's March anti Brexit demonstration in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal Tens of thousands of people march through London EPA People's Vote march – demanding vote on final Brexit deal epa06833265 Thousands of people march through London during a People's March anti Brexit demonstration in London, Britain, 23 June 2018. Protesters are calling for a referendum on the final deal. The protest is taking place on the second anniversary of the Brexit referendum. EPA/ANDY RAIN ANDY RAIN EPA People's Vote march – demanding vote on final Brexit deal Demonstrators at the People's Vote March Getty People's Vote march – demanding vote on final Brexit deal 'Two months too young to decide on my future' REUTERS People's Vote march – demanding vote on final Brexit deal Crowds taking part in the People's Vote march for a second EU referendum at Trafalgar Square in central London. PRESS ASSOCIATION Photo. Picture date: Saturday June 23, 2018. See PA story POLITICS Brexit. 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PRESS ASSOCIATION Photo. Picture date: Saturday June 23, 2018. See PA story POLITICS Brexit. Photo credit should read: John Stillwell/PA Wire John Stillwell PA People's Vote march – demanding vote on final Brexit deal Crowds gather on Pall Mall PA People's Vote march – demanding vote on final Brexit deal A man resembling Britain's Foreign Secretary Boris Johnson, joins EU supporters Reuters People's Vote march – demanding vote on final Brexit deal EU supporters, calling on the government to give Britons a vote on the final Brexit deal, participate in the 'People's Vote' march in central London, Britain June 23, 2018. 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“I cannot imagine any previous generation of Conservatives putting at risk the Union in the way that has now happened,” said the former Tory PM.

“Leaving Europe, carrying Brexit through, will raise strains we know of and strains we haven’t yet thought of. That may well end up with dividing a United Kingdom that has been together for a very long time. It is a thoroughly bad idea.”

Once adversaries in the House of Commons, Blair and Major paid a joint visit to the Irish border during the 2016 EU referendum campaign to highlight the risk that Brexit poses to the peace which they played a significant role in achieving.

Tony Blair: ‘This is why Labour must not agree to this election ploy until the situation is dealt with’ (PA)

Mr Blair said that the deal proposed by Mr Johnson would create "either a hard border between Northern Ireland and Britain or a hard border between the north and south of Ireland.

"It is a shame and an outrage that peace in Northern Ireland is now treated as some disposable inconvenience to be bartered away in exchange for satisfying the obsession of the Brexiteers with wrenching our country out of Europe," said the former Labour premier.

“Either Northern Ireland and its hard-won peace is sacrificed on the Brexit altar. Or we end up in the bizarre situation where Northern Ireland stays in Europe’s trading system and Great Britain leaves with a hard Brexit which itself requires years more of Brexit negotiations and distraction from the real issues facing the country.”

Sir John said a customs border in the Irish Sea would play on the fear of the people of Northern Ireland that they are being “ignored and maltreated”.

“Those fears are very real. And they need to be addressed and they need to be assuaged,” he said.

“There's a whole generation of people in Northern Ireland who have no memory of what life was like before the Good Friday Agreement.

“No-one under the age of 20 would have any memory of the violence and death that once engulfed their neighbourhoods. I hope and pray they never do.”

Sir John said that another “powerful” reason for a confirmatory referendum on any deal was changes in the electorate over the three and a half years since the 2016 vote.

“There are two million people who voted in that referendum who sadly are no longer with us,” he said. “And two and a half million young people who are now on the register who may have very different views about our future in Europe.

“Now they are old enough wish to express their views in a referendum as to the future of their country and their prospects and their life.”

Mr Blair said: “Whatever is the outcome- no deal or bad deal - it should not pass without the final say resting with the people.

“These Brexiteers talk about the will of the people. But in 2016 our knowledge was necessarily limited. Now, three years on - three years of mess, misery and mayhem - when our knowledge is vastly expanded by experience, how can it be undemocratic to ask the British people their final opinion?