The Conservative Party Chairman has been accused of peddling “nonsense” to grassroots Tories in a conference call intended to win support for Theresa May’s Brexit deal.

Brandon Lewis told local Conservative Association chairmen that the proposed deal contained a “very, very high legal bar” requiring the EU to agree a trade deal before there was any need for a Northern Ireland backstop.

Article 184 of the Withdrawal Agreement says the EU must use its “best endeavours” to agree a trade deal before the end of the transition period, but lawyers and Brexit-supporting MPs have argued that the phrase is legally worthless.

There were also claims that Tories with hostile questions were cut off before they had a chance to put them to Theresa May.

The Prime Minister held a 45-minute conference call with around 300 constituency chairmen on Friday afternoon to sell her Brexit deal to them, which was chaired by Mr Lewis.

Concerns about her proposed deal were raised by several callers, including one who felt that the agreement would “lock in” the UK to a “deeply unpalatable” customs union with the EU if the backstop was enforced.

The backstop, which is designed to avoid a hard border in Ireland if no trade deal is agreed before the transition period ends in December 2020, would keep the whole of the UK in a customs union with the EU.