'Very significant' political figures in the US won't tolerate Ireland being damaged in the Brexit process, Mary Lou McDonald has said.
She says the Boris Johnson and the Tories are "very, very wrong" if they think they can get it all their own way.
It comes as the Taoiseach is due to speak to Boris Johnson later to discuss the Brexit developments of recent days.
The British prime minister has come under fire at home and abroad over new legislation published today that aims to override parts of the Withdrawal Agreement relating to Northern Ireland - with his government admitting the move will break international law.
Sinn Féin leader Mary Lou McDonald told The Hard Shoulder it's "astonishing" that the British government is being so brazen.
She said: "In our dealings with successive British governments, it's not unusual at all at all for them to enter into an agreement and then walk away from it.
"They have proven themselves absolutely untrustworthy in the whole Brexit debacle from the start: Irish interests... [were] little more than an afterthought to the champions of Brexit."
She suggested that Boris Johnson had to be "almost dragged to a sensible negotiating position by his own parliament", while Brexiteers were 'grudging' in their agreement to protections for Ireland.
However, she said they're wrong if they believe Ireland can be "bullied" or used as a pawn in the Brexit process - highlighting comments from 'very significant' politicians from across the Atlantic.
I urge the EU & UK to uphold the terms of this joint agreement, particularly w/ respect to the treatment of Northern Ireland, in accordance w/ international law. The Good Friday Agreement, which has maintained peace & prosperity for British and European peoples must be preserved. pic.twitter.com/sJgAdAZ0Yz
— Rep. Richard Neal (@RepRichardNeal) September 9, 2020
She observed: "Congressman Richard Neal - who's the chairman of the ways and means committee on Capitol Hill, the committee that will have to clear any trade deal Britain might hope to have with United States - has reiterated overnight the absolute necessity not to incur damage to Ireland.
"Words to that effect are also coming from one of the presidential hopefuls - Joe Biden's campaign.
"If the British Tories think they simply get it all their own way and they can unilaterally walk away from international commitments... I'm afraid they're very, very wrong."
Deputy McDonald said it's important Micheál Martin now talks to Boris Johnson - but suggested the call should have happened 'as a matter of urgency' after the story about the new legislation emerged on Sunday night.
She reiterated that the Northern Ireland protocol is the "basic protections we need", and that the UK government cannot unilaterally "put that through the shredder".
Earlier, Tánaiste Leo Varadkar urged two of the UK's highest ranking officials to ‘consider their oaths’ amid the ongoing controversy over Westminster’s plan to row back on the Brexit Withdrawal Agreement.
