Brexit Secretary Dominic Raab said Sunday that any extension to a proposed transition period after Britain leaves the European Union must be strictly time-limited or have a "route out".
"There needs to be something which allows us to control how long we are there for to avoid any sense that we are left indefinitely in a sort of customs union limbo," he told the BBC.
"That wouldn't be acceptable."
Raab added: "It would be rather odd if we ended up in that bridging temporary mechanism without a route out, so it could be time-limited, there could be another mechanism."