Commons leader Andrea Leadsom has failed to guarantee that Parliament's Easter break will go ahead as planned.
The House of Commons is not due to sit for two weeks in April - after the UK is scheduled to leave the EU on 29 March.
But Mrs Leadsom told MPs that the recess period remained subject to the process of agreeing new legislation.
Her Labour counterpart, Valerie Vaz, asked her if there were plans for the break to be cancelled.
"I understand some civil servants have been told that their leave is cancelled during that time," Ms Vaz said in the Commons.
Mrs Leadsom replied: "We always announce recesses subject to the progress of business, and that remains the case for the time being."
However, she said she was "confident" the necessary secondary legislation would be passed before 29 March.
Mrs Leadsom also told MPs that over three-quarters of the statutory instruments (SIs) needed before Brexit day had been tabled in Parliament.
Statutory instruments are a type of secondary legislation that allow ministers to change the law without passing a full piece of primary legislation.
Last month, Mrs Leadsom said the EU may be prepared to give the UK extra time to finalise its Brexit preparations.
"I am absolutely certain that if we needed a couple of extra weeks or something, then that would be feasible," she told BBC Newsnight.
Parliament is meeting this week after MPs' February break was cancelled to find additional time for Brexit-related laws.
The SNP's Pete Wishart said MPs had "given up skiing holidays and trips to their villas for barely-debated SIs".
"It seems like the Easter recess is under threat and isn't particularly safe now," he said.
He added that cancelling the break this month had cost "God knows how much money" and inconvenienced parliamentary staff.
Mrs Leadsom said she would "look into" notifying MPs about the costs of running Parliament during the February recess.