“Intolerable risks” at the most hazardous parts of the Sellafield nuclear site are being exacerbated by poor performance, substandard equipment and staff shortages that make the facility even more dangerous, according to a report by MPs in Westminster.

The UK’s public accounts committee (PAC) also raised concerns about the proliferation of non-disclosure agreements to settle staff whistle-blowing complaints about safety and bullying at the site, located on the Cumbrian coast about 170km from Ireland. It said safety concerns and galloping cost overruns were “simply not good enough”.

The committee has released a report on the £136 billion (€162 billion) clean-up job at Sellafield, a former reprocessing and power plant that now essentially operates as a nuclear dump. It said the clean-up of the site is too slow and management keeps missing targets.

It highlighted problems at decrepit buildings such as the Magnox Swarf Storage Silo (MSSS), which has leaked hazardous nuclear pondwater into the soil for seven years. The committee said it was enough to fill an Olympic swimming pool every three years.

The committee accused Sellafield Ltd, the company that operates the site on behalf of the British state, of “underperformance” by taking too long to clear crumbling old buildings such as the MSSS. Its report said the “consequence of this underperformance is that the buildings are likely to remain extremely hazardous for longer”.

It complained that the timeline given by the company for clearing Sellafield’s most dangerous buildings has slipped by 13 years since 2018. The leaking MSSS is being slowly emptied of its lethal material, but the PAC said it needs to be removed 24 times faster than it was last year within a decade, if it is to hit targets.

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“The intolerable risks presented by Sellafield’s ageing infrastructure are truly world-class,” said Geoffrey Clifton-Brown, the Tory MP who chairs the PAC. “When visiting the site, it is impossible not to be struck by the fact that one can be standing in what is surely one of the most hazardous places in the world.”

The PAC found that management needs to “fundamentally transform how the site functions”. It is already estimated the clean-up of the site will take at least 100 years. Sellafield told the PAC it had made progress in some areas.

The report also warned management must do more to “build a culture where all employees feel able to raise concerns and report poor behaviour”. The PAC was told the company had used non-disclosure agreements 16 times in the last three years when settling staff claims.

In response to the report, David Peattie, the chief executive of the UK’s Nuclear Decommissioning Authority, said: “We welcome the scrutiny of the committee and their report. We will now look in more detail at the recommendations and consider how best to address them. We take the findings seriously and the safety of the site and the wellbeing of our people will always be our highest priorities.”

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Alison McDermott, a former executive at Sellafield who fought a legal battle with the company after she made a whistle-blowing complaint about safety and bullying, said the PAC report “vindicates everything I said” about a “toxic and dangerous” culture at Sellafield.

She said “Ireland is not safe” due to the way the site is run: “This is not a British problem – it’s a threat to everyone across the Irish Sea. The Irish Government must wake up.”

The Irish Government once sued Britain over safety fears at Sellafield. It is believed the State made no submissions to the UK’s PAC as part of its latest inquiry into the site.