IN Brief:
- The Public Accounts Committee estimates that each further year of delay could add up to £420m to lifetime restoration costs.
- Full decant and extended occupied refurbishment have sharply different cost and duration ranges.
- A seven-year initial works programme faces a proposed £3bn cap, with uncosted enabling works and governance questions outstanding.
The Public Accounts Committee has warned that another year of delay in decisions about the Palace of Westminster’s restoration could increase the programme’s lifetime delivery cost by up to £420m. MPs are pressing for a choice on how the Palace will function during major construction, when ageing services, fire safety systems, and historic fabric must be addressed together.
Published on 4 November, the committee’s report examines the cost and governance of the Restoration and Renewal programme as the Commons and Lords consider reducing four proposed delivery approaches to two. A vote originally expected before Easter 2026 has yet to take place. According to the committee, delaying the decision until the end of the year could add up to £290m to the estimated programme cost, while uncertainty over the construction strategy risks weakening supplier confidence.
Two approaches have been recommended for further development. Under a full decant, both Houses would leave the Palace for much of the restoration, with an estimated programme cost between £11.1bn and £15.6bn and an indicative duration of 19 to 24 years. The other option, Enhanced Maintenance and Improvement plus, would keep more parliamentary functions within the building while work proceeds in phases. Its cost range is £19.5bn to £39.2bn, with an estimated duration of 38 to 61 years.
Those estimates are broad because the extent of temporary accommodation, access, protection of historic structures, and the sequence of intrusive works differ substantially between the options. A full decant can create longer uninterrupted construction areas, but demands suitable facilities elsewhere for parliamentary operations. Occupied refurbishment restricts access and requires additional separation between working areas and construction activities, potentially extending the period over which temporary services and protective measures remain in place.
Two further approaches were assessed but are not recommended for continued development at this stage. Continued Presence was costed at £14.4bn to £22bn over 33 to 45 years, while Enhanced Maintenance and Improvement was put at £23.3bn to £56.3bn over 52 to 84 years. Those ranges represent early options assessments, not approved construction budgets, and Parliament has yet to choose its final method of delivery.
The Palace currently costs around £1.5m a week to maintain, with that figure expected to rise to £2m. This ongoing expenditure is distinct from the estimated £420m increase in lifetime restoration cost associated with every additional year of programme delay. Continued maintenance can keep parts of the estate functioning, but it does not amount to a comprehensive renewal of deteriorating infrastructure. The National Audit Office has previously identified problems involving mechanical and electrical systems, fire safety, asbestos, and the condition of the historic fabric.
The Palace’s electricity distribution, plumbing, ventilation, and other essential services are embedded within a protected, functioning heritage building. Replacing them can require intrusive surveys, temporary supply routes, controlled isolations, and careful reinstatement of affected spaces. The committee wants firmer cost estimates for isolating, decommissioning, and relocating services because those tasks can govern access to the main work areas and the sequence of subsequent packages.
Parliament is also being asked to authorise an initial seven-year phase of works capped at £3bn, including a proposed £500m contingency. The committee wants the remaining cost estimates and available contingency set out more clearly before commitments increase. Three outstanding areas are riverside security, the isolation and diversion of essential services, and restoration of the medieval cloister court. Each affects an identifiable construction interface: site security and access, utilities needed during a phased shutdown, or the protection of sensitive historic structures.
Temporary accommodation is another major interface. Options under consideration envisage alternative facilities for the Houses while parts of the Palace are unavailable, and the readiness of those spaces will govern when restoration work can begin in earnest. If the buildings used for parliamentary functions are not available at the required time, the programme may have to adjust the decant sequence or prolong interim arrangements. The committee has called for clearer plans explaining how parliamentary staff and members will be engaged in choices that directly affect their workplaces.
The period over which restoration is delivered will shape procurement as well as direct expenditure. Specialist contractors covering heritage fabric, mechanical and electrical renewal, fire protection, scaffolding, and temporary works need decisions on phasing before allocating teams and committing supply capacity. The committee identifies uncertainty over the delivery route as a risk to supplier confidence; the published ranges should not be read as tender prices or evidence of an approved construction overspend.
The committee calls for additional scrutiny of programme spending and delivery, including proposals for a dedicated parliamentary select committee overseeing Restoration and Renewal. Clearer arrangements are also needed between the Client Board, Client Team, and Delivery Authority, particularly where programme changes affect access, operational continuity, cost, or schedule. Those decisions will determine whether initial enabling works produce a usable sequence for the larger restoration rather than separate packages with unresolved interfaces.
MPs and peers must first decide which delivery options to develop and whether to authorise the proposed initial works. Until that choice is made, the location and readiness of temporary parliamentary accommodation, the scope of service diversions, and the sequencing of heritage repairs remain significant uncertainties in a programme already carrying substantial delay-related cost exposure.
