MPs on the Brexit select committee are seeking an extension of the article 50 process beyond next March

Britain’s customs system will not be ready in time for the start of its new relationship with the European Union at the end of 2020, according to a damning report presented in secret to senior cabinet ministers last week.

The readiness assessment, drawn up by senior civil servants, was given to Theresa May’s Brexit war cabinet on Tuesday afternoon. But ministers did not get a chance to study it properly before the meeting was cut short by a Commons vote.

The cabinet was told it would have to sign up in Brussels this week to a transition phase lasting 21 months from the date of Brexit next March, with a new trade deal kicking in at the end of December 2020. David Davis, the Brexit