Rebuilding Parliament could cost £40 billion but may be essential to end the risk of a devastating fire destroying the historic site, Parliamentary authorities have warned.

MPs and peers have been presented with options to restore Parliament, which include moving MPs out entirely while refurbishment takes place.

Conservatives insisted the huge potential costs could not be justified. Jesse Norman, Shadow Leader of the House of Commons, said a report setting out proposals to preserve the Palace of Westminster “is asking parliamentarians to approve eye-watering expenditures of up to £19 billion pounds on a project with unclear governance, limited scrutiny and low confidence of effective project or cost management.”

Parliament’s restoration and renewal client board has put forward two options – one for a “full decant”, which would see both houses move out of the Palace of Westminster while work takes place, and another where the palace would be worked on in stages.

The full decant would last up to 24 years and cost up to £15.6 billion, while the other option would take 38 to 61 years and cost up to £39.2 billion. Those figures include inflation.

The board said: “A decision is needed now on starting restoration work. Most of the building dates from the Victorian era and some parts are much older.

“Over the decades, its fabric and its services have deteriorated and require substantial repair or replacement. We are beyond the point where putting off these major works is sustainable.”

MPs and peers have also been asked to agree to initial restoration works lasting seven years, at a cost of up to £3 billion. That work could start in 2026 if approved.

The board will ask them to choose between the final two options by mid-2030.

The phase one works will include refurbishing the inside of the Victoria Tower, building a jetty on the Thames for deliveries by river and starting underground construction on tunnel shafts.

A full decant would see Commons business start to move to the so-called Northern Estate – outside of the palace but close by – while the House of Lords would move to the nearby QEII conference centre from 2032.

Although repairs would cost eye-watering sums, the board warns that the current cost of repairing and maintaining the Palace of Westminster is “unsustainable” at a £1.5 million weekly cost.

The heating doesn’t work in large part of the House of Lords, there are significant problems with the sewerage system and there have been36 fire incidents, 12 asbestos incidents and 19 stonemasonry incidents since 2016.

The client board said restoration would bring “significant economic benefits” and support thousands of jobs and apprenticeships across the UK, from modern construction specialists to traditional craftspeople.