Multibillion-pound Westminster repairs could cost more than first estimated, commons clerk warns

The multibillion-pound renovation of the Palace of Westminster could cost more than current estimates, the Clerk of the House of Commons has warned.

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 the Commons and Lords move out for up to eight years while repairs are carried out – at an estimated cost of around £3.5 billion.

The proposals, which would have to be approved by Parliament and the Government, could see a temporary Commons chamber in the courtyard of the Department of Health's current offices in Whitehall, while the Lords would sit in the nearby Queen Elizabeth II conference centre.

The Joint Committee on the Palace of Westminster rejected more expensive options of trying to carry out repair work without leaving the building, or completing the renovations in stages with each chamber moving out in turn.

Mr Natzler said the cost of renovations could either rise or fall as the parliamentary authorities were likely to find things out about the building they did not previously know once work gets under way.

Appearing before the Commons Public Accounts Committee (PAC), Mr Natzler said: "We will certainly find things we don't know, there are known unknowns.

"£1 billion of those figures is attributable to, in the first place, inflation, which to a non-accountant doesn't sound like a financial cost, it's just the business of putting it off and figures go up.

"And a large slice is attributable to VAT, well VAT is simply a transfer from one part of the public sector to another.

"So those figures are of course frighteningly large, you are used to them in dealing with aircraft carriers and nuclear submarines and so on.

"So yes, the figures could be higher, the figures could be lower, these are orders of magnitude for comparative purposes."

The Commons Clerk, who is responsible for Parliament's spending of public money, dismissed the option of politicians staying in the building, with works to patch it up to basic standards taking around 32 years at a cost of between £4.9 billion and £7.1 billion.

"It is actually not feasible that the Palace would continue to house both Houses of Parliament, it's not going to happen," Mr Natzler said.

"Asbestos will get into the air and you will close the place down and have an emergency decant at huge cost, unplanned, and then have to start again.

"It is a purely technical option which our advisers did only because we paid them to do it."

Mr Natzler said that even if a full decant were to take place in five or six years time, the Palace would survive that long "on a wing and a prayer" with the risk of systems failures mounting every year.

"I cannot guarantee we will be here for the next five or six years," he said.