Jeremy Corbyn has said he agrees with President Macron of France that the backstop, designed to avoid a hard border between the UK and the Republic of Ireland after Brexit, is indispensable.
The Labour leader said the question of the Irish border was “fundamental” to a lot of things. “The Irish peace process was an enormous step forward. It’s an international treaty. It’s an international agreement,” he said.
“It cannot be negotiated away by Boris Johnson or anyone else.”
The prime minister has said the backstop is “undemocratic” and must be removed from the withdrawal agreement or the UK will leave the EU without a deal.
Mr Corbyn was speaking during a visit to a farm in Cumbria to highlight his opposition to a no-deal Brexit.
