Boris Johnson hints he may not support Rishi Sunak’s Northern Ireland deal

Under the Eurosceptic proposals the UK government would pass legislation creating a new export certification and tariff collection system for exporters to the EU. Photograph: Clodagh Kilcoyne/Reuters

Boris Johnson has hinted he may not support a proposed deal over the Northern Ireland protocol from Rishi Sunak, heaping pressure on the prime minister to revive a controversial bill that would unilaterally override parts of the Brexit treaty.

His intervention came on Thursday as it emerged that lawyers advising Eurosceptics in the Conservative party submitted fresh proposals to Sunak to end the rule of EU law in Northern Ireland, one of the major sticking points in the UK-EU negotiations over the protocol.