The first images have been released of the proposed temporary home for MPs during restoration work in Parliament.
Architects plan to recreate the current chamber of the House of Commons, including the green benches on which MPs sit, at a new venue in Westminster.
The move to Richmond House, the former home of the Department of Health, will not happen until 2025 at the earliest.
The refurbishment of the current Palace of Westminster, due to cost £4bn, will not now be completed until the 2030s.
The repair work is likely to take between five and eight years longer than previously anticipated.
Legislation has been published to create an Olympics-style delivery body to oversee the project after MPs voted last year to vacate the Palace of Westminster, which houses the Commons and the Lords.
However, many members are concerned about the estimated cost of the project and want the proposed move to another venue to be as short as possible.
Speaking at Prime Minister’s Questions, Theresa May said the refurbishment would allow the historic Palace of Westminster to be safeguarded for future generations.
“But it is imperative that Parliament keeps the total bill as low as possible,” she added.
The proposed temporary chamber will be similar to the current one, complete with leather benches and an adversarial layout, but will be more accessible.
Under plans opened for consultation, nearby buildings will be improved and a six-storey office block for MPs constructed at an estimated cost of £1.4bn to £1.6bn
What future works are planned?
The work is expected to include replacing old cabling, installing a new sewage system and improving disabled access to the estate.
Both the Commons and Lords agreed in early 2018 that the most cost-effective way to carry out the upgrades would be for them to move out whilst the works are being done.
A detailed design brief and budget will need to be signed off by Parliament, with more exact costs known once the new body has made its business case.
In 2015, the Independent Options Appraisal estimated the one-phase programme would cost between £3.52bn and £3.87bn, at 2014 prices.
But Sir Edward Leigh, a critic of the project, said the proposed “decant” may not take place until 2028 and much-needed building work could not be delayed until then.
Raising the issue in the Commons, he expressed concerns a large part of the “award-winning, listed” Richmond House would be demolished to accommodate the replica chamber.
“Will her government ensure that for reasons of safety we get on with the work as quickly as possible and when a decant is necessary it is for as short a time as possible?” he asked.
The Palace of Westminster, the home of Parliament, is in danger of going the way of Notre Dame.
The electrical system is iffy, the pipes leak, the stonework is crumbling and the roofs need replacement.
It is simply not possible to do the necessary work with MPs and peers still working in the building – the deterioration is now happening faster than can be remedied at weekends and during holidays.
The new delivery authority will be responsible for drawing up full details of plans and costs, which will have to be approved by MPs.
A committee of MPs and peers will also be set up to scrutinise the spending plans alongside the Treasury.
Former Clerk of the Commons Lord Lisvane said work was needed urgently as it was “a matter of time” before something happened to the parliamentary estate.
“I’m afraid there has been a certain amount of foot-dragging and my message now would be emphatically, crack on with it,” he told the BBC.
Labour’s Meg Hillier, who chairs the the Public Accounts Committee, said a final cost for the works would only be known once MPs move out but would be “many billions” of pounds.
She added that it is hard to be “absolutely sure” when MPs would move back in once the repairs begin.