David Natzler said there are “known unknowns” in the Houses of Parliament, which faces a growing risk of a “catastrophic event” unless ageing mechanical and electrical services are renovated.
A committee of MPs and peers last year recommended that MPs and Lords move out for up to eight years while repairs are carried out – the so-called “full decant” option estimated by Deloitte to cost between £3 billion and £4.3bn, with the most likely figure around £3.5bn.
A study by Deloitte last year highlighted the appalling condition of the Palace of Westminster, with potentially deadly fire risks, collapsing roofs, crumbling walls, leaking pipes and large quantities of asbestos.
The study also warned that if politicians had refused to leave the building, patching it up to basic standard would have taken more than 30 years and would have likely cost between £4.9 billion and £7.1 billion.
A temporary Commons chamber may be set up in Whitehall.