More asbestos has been discovered in Parliament, the BBC has learnt, as MPs come under pressure to sign off on a major revamp of the crumbling home of UK democracy.

Known asbestos items in the Palace of Westminster and wider parliamentary estate, such as insulation, roofing, floor tiles and ropes, now number more than 1,650 – an increase of 500 since 2021.

It comes as the government considers holding a vote on refurbishing Parliament, which could cost up to £40bn and take 61 years, after years of indecision and delay.

The Commons public accounts committee this week warned it was “crunch time” for Parliament’s restoration, with every additional year of delay costing taxpayers £420m.

More asbestos items were found during surveys in preparation for the long-awaited refurbishment project, parliamentary authorities said.

Asbestos has been identified as one of the main reasons for the refurbishment, given the dangers to human health when its fibres are airborne. While asbestos is largely fireproof, surrounding fire and heat can release fibres over long distances.

In the past five years, 700 items of asbestos have been removed from Parliament but the total has still risen, a Freedom of Information request by the BBC found.

Under Health and Safety Executive guidelines, most of it is classed as low risk in concealed areas, meaning it is less likely to be disturbed, but almost 200 items are classed as medium risk meaning they may require remedial works.

A spokesperson for UK Parliament said its “absolute priority is the safety of the those who work on and visit the parliamentary estate” with improved asbestos monitoring, new awareness training, and plans to further remove it.

Kris Gledhill, the son of former Labour MP Alice Mahon who died in 2022 of malignant mesothelioma – a type of cancer linked to asbestos exposure – told the BBC “asbestos should never be considered low risk”.

“A precautionary approach should be adopted: this includes assessing the fact that in addition to the risks from buildings deteriorating over time, there are also risks of damage from extreme weather events, floods and fire, and from disturbances caused during renovation and maintenance work,” he said.

“Alice was well aware of the risks relating to asbestos and mesothelioma,” he added.

“She was able to identify two workplaces where she might well have been exposed, one of which was the Palace of Westminster.”

The Commons authorities told the BBC “an asbestos-free building cannot be achieved in practice” because that would require demolition or extensive damage to the fabric of the building.

Dr Hannah Moody, chief executive of charity Mesothelioma UK which campaigns on asbestos-related diseases, said she backs introducing a national asbestos register and the phased removal of asbestos from public buildings.

“Although asbestos was banned in 1999, it remains present in many public buildings across the UK and continues to cause serious illness and work-related deaths, including from the aggressive cancer, mesothelioma,” she said.

Workers should be given health and safety advice to manage the risks, she added.

The findings come as the Commons Public Accounts Committee on Wednesday published the results of its inquiry into Parliament’s restoration and renewal (R&R), external programme, which is exploring options to revamp the site.

Geoffrey Clifton-Brown, the Conservative MP who chairs the committee, told the BBC that if a small fire broke out in the building “the whole lot would go up” – with 24-hour fire patrols in place.

“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,” he added.

He said this was a “real and rising… grave risk” and criticised “a political allergy to gripping the nettle” of refurbishing Parliament after years of delay.

The committee said there was enough information for MPs and peers to vote on a way forward before the end of this year.

The BBC understands government whips have discussed holding a debate and vote by then, but no date has been scheduled.

This vote would decide whether to proceed with up to £3bn of initial works and narrow down four current options, ahead of a final decision by 2030.

One proposed option would see MPs and peers move out of the site for up to 24 years from 2032, costing up to £15.6bn.

Another involves moving only the House of Lords out of the building, costing £39bn and taking 61 years.

Among the “critical” setbacks the committee identified were an overcomplex decision-making process and delays in acquiring a temporary home for the Lords in the nearby Queen Elizabeth II conference centre, which is owned by the government.

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