A Labour former Cabinet minister will seek to force major changes on the Brexit Bill claiming he has a mandate despite being an unelected peer.
Peter Hain is to demand the UK remains in the single market and retains a completely open border between the North and the South when legislation reaches the House of Lords on Monday.
Mr Hain will attack UK Prime Minister Theresa May for failing to represent the 48% who voted in favour of Remain and argue her exit strategy could lead to a "Trump Brexit" that turns the UK into a low tax haven.
He will attempt to head off criticism about his plans to water down the Bill by insisting he is reflecting the views of most Labour voters.
Mr Hain will argue: "Critics say 'what right have I, an unelected peer, to oppose this Bill or even to seek radically to amend it?'
"But I was appointed by my party. And in the referendum, two thirds of Labour electors voted to Remain. That's what I am reflecting, that's my mandate.
"Especially as the Prime Minister is behaving as if she only represents the 52% of citizens who voted Leave. I don't deny they won, or that the outcome has to be respected. But what about the 48% who voted Remain?
"The truth is the country was split down the middle - and still is. If the Prime Minister were really acting in the national interest, she would be representing them too. She would be pursuing a 'one nation Brexit' not a partisan hard, right wing Brexit."
Mr Hain , a former Northern Ireland Secretary, will warn the peace process could unravel under Brexit and has tabled an amendment, backed by another former holder of the post, Lord Murphy of Torfaen, calling for the border to remain open.
He will insist: "A 'one nation Brexit' would also mean guaranteeing a completely open border between Northern Ireland and the Republic - no security checks, no controls, physical or electronic.
"Otherwise I believe the peace process could unravel, as indeed Bertie Ahern, the former Taoiseach and so important to the success of that process has said."
Mr Hain will also push for a vote on keeping Britain in the single market, warning that severing ties with its biggest trade market will have a "devastating" impact on the economy.
The peer, who has previously said he will vote against the European Union (Notification of Withdrawal) Bill, will argue a deal could be done to keep Britain in the single market that included restricting free movement rules to people who have jobs.
He will argue: "Cutting us off from our biggest market, where nearly half our trade is done, will have devastating consequences for the economy, for jobs and for millions of individual citizens' lives.
"We now learn that if we cannot get the EU trade deal we want, the Government threatens, in a 'Trump Brexit', to make Britain a low tax 'haven' with lower labour and environmental regulation, in an attempt to attract foreign firms once we have left the EU.
"That would also mean continued shrinking of the state, even more savage cuts in public services and even greater inequality, hitting hardest the poorest and most vulnerable citizens."