He said he had been horrified to find out the cost of the Portcullis House greenery and accepted the taxpayer was being "fleeced".

The deal has been in place for 12 years and covers care and maintenance of the trees, which shade dining areas in the building's glass-topped atrium.

But Mr Bercow said it should be scrapped immediately, if contractually possible without adding more costs, but no later than September.

In an interview with The House magazine, he said: "I was horrified by it.

"Inevitably and understandably it will cause people out there to think these people are living in another universe. I think the contract should absolutely be revisited. If we are going to have trees, they absolutely shouldn't be trees that cause us to fleece the taxpayer in this way, and that must change at the earliest opportunity."

Mr Bercow also conceded that there were some grounds to argue that the daily prayer session in the Commons was discriminatory.

But though he said he would not stand in the way of a review if sufficient MPs wanted one, he said he wanted to keep what was a "reasonable and generally popular" tradition.

Focus was put on the prayers - which MPs must attend to secure a seat for some high-profile parliamentary sessions - after a court ruled prayers could not be part of local council business. The ruling does not apply to the Commons, which sets its own rules.

The Speaker also called for annual party conferences to be cut to a long weekend so that the Commons could sit without a break from September.