According to the BBC
The report says that Liam Fox, Michael Gove, and Dominic Raab are among those ministers voicing out concerns about the UK remaining in the customs union for an open-ended period. They remain of the view that a backstop agreement needs to be temporary and there has to be an end/solution to it without letting it drag on indefinitely.
This will be a key sticking point when May tries to get her Chequers proposals through a vote in parliament.
