The British Parliament's landmark as part of the Palace of Westminster in the heart of London was completed in 1859 and has been a focal point of new year celebrations in Britain and around the world.
A cross-party House of Commons Finance Committee's report says it would only cost 4.9 million pounds to "prevent the clock from failing" but that the cost could rise to 40 million pounds if Big Ben's other problems are not dealt with at the same time.
The work could see the clock shut down for four months, the longest known silence in its 156-year life. In 1976, repairs saw the clock stopped for 26 days over nine months.
The committee's report, seen by 'The Sunday Times', says Big Ben has "chronic problems" with the bearings behind the hands and pendulum, adding: "Either could become acute at any time, causing the clock to stop - or worse."
There is also severe metal erosion, cracks in the roof and other structural defects, the reports says.
"There are major concerns that if this is not carried out within the next two to three years, the clock mechanism is at risk of failure with the huge risk of international reputational damage for Parliament," the report said.
It also adds that, were the clock-hand to fail, it could take up to a year to repair because of the scaffolding needed.
The 315ft tower is also due to get a visitor centre and a lift installed to save people the 334-step journey.
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