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Kirsty Wigglesworth, Associated Press
Scaffolding surrounds the Houses of Parliament in Westminster in London, Thursday, June 18, 2015. Britain's Parliament is falling apart. That's not a political criticism, but the judgment of a report that says the crumbling 19th-century complex needs repairs that could take three decades and cost up to 7 billion pounds ($11 billion).

LONDON — The seat of British democracy is creaky, crumbling and at risk of falling apart.

That's the judgment of a report published Thursday that says the 19th-century Houses of Parliament complex beside the River Thames — one of Britain's most famous buildings — needs repairs that could take three decades and cost up to 7 billion pounds ($11 billion).

The report, commissioned by parliamentary officials and conducted by consultants led by Deloitte Real Estate, said the building has not undergone major restoration since 1950. It said "fundamental renovation can no longer be avoided" to protect a structure that is part of the "U.K. brand, instantly recognized and appreciated around the world."

"If it doesn't happen, we can't guarantee that this building will be here for future generations," Richard Ware, Parliament's director of restoration and renewal, told Sky News.

The report cited recent episodes including a burst pipe flooding the Committee Room Corridor and part of the ceiling in the Lords chamber falling onto the benches below, and said "the risk of a catastrophic failure is increasing."

The consultants laid out several options. They said that if lawmakers and peers agree to move out during restoration — what the report terms "a full decant" — work could take six years and cost about 3.5 billion pounds ($5.6 billion).

If politicians and staff remain, the most expensive option foresees work taking 32 years at a cost of 5.7 billion pounds, possibly rising to 7.1 billion pounds.

A parliamentary committee will examine the report, and any work is unlikely to begin before 2020.

Most of the Parliament complex was built after a major fire razed its predecessor in 1834, though the oldest section, Westminster Hall, is 900 years old.

The Palace of Westminster, as the buildings are officially known, has been designed a World Heritage Site by UNESCO. But its maze of corridors, leaky roofs and antiquated plumbing make it a challenging workplace for some 2,000 politicians and staff, and the stonework on its neo-Gothic exterior is crumbling.

British legislators last moved from their traditional chambers when bombs fell on the building during World War II, setting the House of Commons on fire.