Brexit: Boris Johnson to override EU withdrawal agreement

Move threatens to collapse talks that PM has said must be completed within weeks

Boris Johnson is drawing up legislation that will override the Brexit withdrawal agreement on Northern Ireland, a move that threatens the collapse of crunch talks which the prime minister has said must be completed within five weeks.

Johnson will put an ultimatum to negotiators this week, saying the UK and Europe must agree a post-Brexit trade deal by 15 October or Britain will walk away for good.