The Houses of Parliament are in such bad condition that the building could collapse without billions of pounds worth of repairs.
An independent report is due to be published laying out a range of options for renovating the Palace of Westminster, all of which would take years and involve vast expense.
A team of specialists were commissioned to come up with practical proposals for change following a study published in 2012.
It showed that unless significant restoration work is undertaken, major, irreversible damage may be done to the Palace.
It is thought the cost of a full refit will be in the billions - Speaker John Bercow has already suggested that £3bn might be a "cautious" estimate. It was reported at the weekend that cost could soar to £6bn.
The bulk of the building dates from the mid-nineteenth century, after the original Palace of Westminster was all but destroyed by fire in 1834.
It remains a titanic monument to the splendour of Victorian Britain, but behind its splendid facade, parliament is now showing its age.
The roof was built from cast iron - cutting edge technology at the time, but now corroded and leaking.
Stonework has been seriously damaged over the years - the old London smog ate away at the walls and in many places they have never been repaired.
Underground passages that were designed for ventilation now house miles of cables - electricity; heating and telephone lines are all crammed in together.
It is thought that MPs will be told that unless they are prepared to vacate the building while the work is going on, it will be more costly.
Such a move is likely to be viewed as unpalatable by many parliamentarians.
At a time when Westminster politics is not held in high regard, there is also a danger that voters will view the renovation of the building as MPs feathering their splendid nest.
That means that while the scale of the physical refit is staggering, the challenge of selling the project to a sceptical public may be still more imposing.