However, Michael Forsyth, a long-serving Conservative peer currently standing for the position of House of Lords Speaker, announced the anticipated cost at a recent hustings.
He told peers “the latest proposal would cost £15 billion” before adding: “I believe that’s secret, by the way.”
Two people with knowledge of the proposals told POLITICO they believed the figure cited by Forsyth was accurate, but sat within a range of official estimates. One said the upper estimate was likely to be higher.
Forsyth was referring to the plan known as “full decant”, under which MPs and peers would move out of parliament to another location for several years while works including asbestos removal and rewiring are carried out.
Successive governments have delayed the wholesale renovation of parliament amid fears of a public backlash over the cost. It was estimated at between £7 billion and £13 billion in 2022, but has since risen.
Forsyth’s remarks at the hustings, where he faced off against crossbencher Deborah Bull, were recorded in full for a podcast by the Hansard Society.