A parliament spokesman said on Tuesday: "While the tower itself is structurally sound and does not require works to improve its stability, other works are now a matter of urgency," Xinhua news agency reported.
"Cracks have developed in the masonry, the cast iron work on the roof and belfry is corroding, and leaks have caused damage internally," he said.
"There is evidence of serious condensation, leading to problems with damp, cracked plasterwork, and rust. Corrosion to the bell frame has caused one of the feet supporting the quarter bells and Big Ben to split," the spokesperson added.
A three-year program of work will begin early in 2017. It will mean the clock being switched off and the bell silenced for a period of time while the work is carried out.
Despite attention from specialist clock makers on a daily basis, it is estimated that if problems are not addressed soon, there is a high risk that the clock will fail.
The project represents the biggest program of works in the history of the tower. The last major overhaul of the clock took place over 30 years ago.
Significant elements of the tower will be restored to their original design and LED lighting will be installed to increase energy efficiency to reduce the tower's environmental impact.
Steve Jaggs, keeper of the clock, said: "In order to keep the clock ticking, we must now take the time to thoroughly inspect and restore it."