The concerns were triggered by the Government agreeing to a compromise which would allow flexibility over the exact day of the UK’s departure from the EU.
Mrs May told MPs that in “extremely exceptional circumstances” the date of March 29, 2019, could be put back – prompting worries that our stay in Europe might be extended “indefinitely”.
The compromise on the EU Withdrawal Bill came as ministers attempted to avoid another humiliating defeat following the one last week when Tory Remainers joined Labour and the SNP apparently in a bid to derail Brexit.
Mrs May was pressed on its potential impact during Prime Minister’s Questions.
Tory defence committee chairman Julian Lewis asked for assurances that the provisions set out in amendment 400 to the Bill to “change the date of our leaving the EU will be invoked only if at all under extremely exceptional circumstances and only for a very short period.”
Mrs May said she was happy to give that “reassurance”, replying: “We’re very clear we will be leaving the EU on March 29, 2019, at 11pm.”
However, she added: “I can assure the House we would only use this power in exceptional circumstances for the shortest possible time.”
Basildon’s Tory MP John Baron pursued the point by asking: “Will she assure the House that, if the power is used at all, it will be used only for a matter of weeks or for a couple of months at most?
“There is a concern that it could indefinitely extend our stay in the EU.”
Mrs May replied that if the power was to be used, it would be only “for the shortest possible time.”
Brexit minister Steve Baker has added his name to the amendment tabled by senior MPs, including Sir Oliver Letwin and leading Brexiteer Bernard Jenkin, which has emerged as a compromise following the Government’s first defeat over the Bill.