Boris Johnson has claimed any Brexit deal must involve the Irish backstop being abolished.
The new British prime minister has addressed the House of Commons for the first time since being formally appointed to his new role yesterday.
It came after he held the first meeting of his newly-appointed cabinet this morning.
Addressing MPs, he reiterated his stance that the UK will leave the EU on October 31st with or without a deal.
Mr Johnson said: "The withdrawal agreement negotiated by my predecessor has been three times rejected by this house.
"Its terms are unacceptable to this parliament and this country."
He then turned to the backstop to avoid a hard border in Ireland.
He argued: "A time limit is not enough - if an agreement is to be reached, it must be clearly understood that the way to the deal goes by the abolition of the backstop.
"For our part, we are ready to negotiate in good faith an alternative - with provisions to ensure the Irish border issues are dealt with, where they should always have been: in negotiations on the future agreement between the UK and the EU.
"I do not accept the argument that says these issues can only be solved by all or part of the UK remaining in the customs union or single market. The evidence is that other arrangements are perfectly possible, and are perfectly compatible with the Belfast or Good Friday Agreement - to which we are of course steadfastly committed."
The EU has repeatedly ruled out scrapping the existing withdrawal agreement, and the prospect of changes to the backstop have been dismissed by the Taoiseach.
They've instead insisted any arrangements to supersede the backstop 'insurance policy' must happen in the context of an agreement on the future relationship between the EU and UK.
Elsewhere, Mr Johnson today said he's tasked cabinet member Michael Gove with 'turbo-charging' efforts to prepare for no deal.
He also stated that the UK will under no circumstances be nominating candidates for a European commissioner role.
The new prime minister also confirmed his intention to introduce legislation to enshrine the rights of EU citizens in legislation, even in the event of a no-deal exit.
Responding to Mr Johnson's first parliamentary address in his new role, Labour leader Jeremy Corbyn warned there's something "eerily familiar" about a prime minister "marching off to Europe" to demand an end to the backstop.
The opposition leader asked: "How does the prime minister think he will succeed where his predecessor failed?"
Mr Corbyn also said in any second referendum on a Brexit deal agreed by Mr Johnson's government that Labour will campaign for remaining in the EU.