Dan Kitwood / Getty Tory rebel remainers warned that they have Theresa May's future in their hands. An upcoming vote on staying in the customs union after Brexit could be treated as a vote of confidence in her leadership. Aides to the prime minister have briefed that she is preparing to surrender on the issue. However, Downing Street insists that she remains committed to cutting customs ties with the EU. UK government will put a new customs proposal to the EU this week, sources tell BI.