The Houses of Parliament risk a "catastrophic event" and even burning to the ground unless at least £4billion is spend on renovations, according to a new report.

Under the scheme MPs and peers could be forced to move out for up to six years.

The report's authors denied accusations of a "vanity project" and warned delaying work to save the historic building from disaster would only cost the taxpayer more in the long run.

But the SNP criticised the findings saying all the option of a new building had been ignored.

MPs and peers did consider moving to temporary rafts on the River Thames.

They found "several problems" however including that any temporary structure would have to be "so large that would need to take up virtually the whole width of the river".

The Joint Committee on the Palace of Westminster also identified "significant security challenges" with a temporary building on the river alongside "issues of noise and nuisance".

They also rejected calls to move Parliament outside London, dismissing "superficial attractions" such as cheaper accommodation and warning that the need for ministers to be close to their departments in Whitehall was too great.

Their proposals, which would have to be approved byParliament and the Government, could see a temporary Commons chamber in the courtyard of the Department of Health's current offices in Whitehall, while the Lords would sit in the nearby Queen Elizabeth II conference centre.

A study by Deloitte last year highlighted potentially deadly fire risks, collapsing roofs, crumbling walls, leaking pipes and large quantities of asbestos.

The committee rejected the more expensive options of trying to carry out repair work while MPs and peers stayed in the building.

SNP MP Alex Salmond said:“The report on the restoration of the Houses of Parliament lacks credibility.

"It does not put all options on the table - it does not consider a new build parliament when it must scrutinise all possible options - and it is based on figures which were proposed in 2014.

“The UK government will effectively be asking taxpayers to pay a Westminster premium to crowbar a modern parliament into a Victorian building at a time of austerity when Tory policy is hitting some of the poorest in society, and political uncertainty when this UK government has no plan for the UK outside the European Union."

No 10 said that the Prime Minister would examine the report before forming a view.