The British taxpayer could face a bill of up to £7 billion to stop the Palace of Westminster "falling down" unless MPs and peers agree to move out, a new report by independent consultants has found.
According to the study, Parliament is in an appalling state of repair - including major fire risks and potential roof collapses.
It recommends a series of options, including politicians staying in the famous building to a "full decant" that would see both chambers emptied and moved to temporary accommodation.
But if MPs and peers remain, the necessary work will take an estimated 32 years and could cost £5.7 billion - with the possibility the figure could hit £7.1 billion.
A third option suggests Parliament be vacated in turn, at a cost of around £4.4 billion.
Fully leaving the heritage site while it is renovated into a state-of-the art building with mod cons would take six years and cost around £3.9 billion.
A joint committee of MPs and peers will now be formed to consider the choices.