The Palace of Westminster is at risk of a "catastrophic event" if delays to a renovation initiative are not resolved, a group of MPs have warned.

The Public Accounts Committee (PAC) has said a Notre-Dame-style fire or the King being plunged into darkness during the State Opening of Parliament were among the "real and rising risks" of continued postponements to the restoration and renewal programme.

Without action, the best case scenario would see the historic building crumble away into managed decline, the committee added.

In its latest report, published on Wednesday, the PAC estimated that the weekly cost of maintenance on the parliamentary estate is expected to grow from £1.5m to £2m in the coming years, warning that each year the programme is delayed will add £420m to the cost of delivering the scheme.

The report comes ahead of a series of votes in parliament to decide the future direction of the restoration programme, which were expected to take place earlier this year but have been delayed.

MPs first voted to leave parliament to allow the building to undergo extensive repairs in 2018, but there has been continued disagreement about whether this should proceed.

Sir Geoffrey Clifton-Brown, chair of the PAC, said that "each kick of the can down the road costs hundreds of millions in public money", and urged those looking to delay a decision further to "imagine the blow suffered by the UK's morale and reputation of some kind of catastrophic failure".

"A lack of action risks, for instance, the chamber being plunged into darkness during the State Opening of Parliament," Sir Geoffrey added.

"Consider the impact of global rolling news footage of Notre-Dame-like flames licking out of the building's roof, resulting in the destruction of our heritage, or worse, injuries or loss of life.

"These are not notional possibilities, but real and rising risks which our committee identified three years ago."

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Several options under consideration

Parliamentarians will be expected to narrow down the number of options for how the refurbishment programme will be carried out from four to two.

The first recommended option, a "full decant", could cost up to £15.6bn and last up to 24 years, while the second proposal, a partial decant, could last more than six decades and cost close to £40bn.

MPs and peers have also been asked to agree on the initial phase of the programme - capped at £3bn - which would focus on moving both Houses to temporary locations, as well as on relocating offices outside the palace.

The PAC, however, has warned that the temporary sites for MPs and peers may not be ready for when they would be required to leave the Palace of Westminster for restoration work to begin - which according to current timescales would be in 2032.

Sir Geoffrey also acknowledged that all options for the programme would "involve extremely high figures with very big ranges".

A parliament spokesperson said the PAC report "provides welcome scrutiny", adding: "Work is already happening across the parliamentary estate to ensure the ongoing safety of those working here and visiting."