Business in the House of Commons was delayed for an hour after water started pouring from the ceiling of the chamber.
Staff were seen using buckets to catch water dripping around the famous green benches.
Speaker of the House of Commons Sir Lindsay Hoyle said the leak had been caused by an aid conditioning unit.
He said: “The air conditioning unit is not the one for the chamber but from an office nearby.
“I’ve been assured that it’s safe for us to sit in the chamber. All of today’s business has protected time and so no debates have been curtailed as a result of the delayed sittings.”
Police officers were seen heading into the chamber with blankets and MPs said the leak appeared to be “just in front of the despatch box”.
A message on the annunciator monitors in parliament said: “Today’s sitting is delayed due to a water leak in the chamber. Revised sitting time to be announced.”
The Commons was scheduled to start at 2.30pm with prayers followed by work and pensions questions.
A House of Commons spokesperson said: “Due to a water leak in the House of Commons chamber, the start of business was delayed.
“Maintenance staff took action to resolve the situation, and the house is expected to sit from 3:30pm.”
The Palace of Westminster is in a state of disrepair and urgently needs major restoration works.
Just a few months ago MPs were issued with a warning about the risk of “falling masonry” on the parliamentary estate.
Officials had to introduce “exclusion zones” alongside the north side of the historic Westminster Hall.
Meanwhile, a recent report found the works needed to save the palace could cost up to £22 billion and last 76 years.
The project has been subject to a number of set backs and a desire from some MPs to remain in the historic building.
It comes after HuffPost UK revealed that renovation work had to be halted and the Health and Safety Executive launched an investigation after a asbestos leak last October.
Up to 117 people were potentially exposed to asbestos in the leak over four days during works on the Speaker’s bedrooms.