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Sadiq Khan today ordered an inquiry into the finances of the Olympic Stadium after it emerged that the total cost of converting the arena for West Ham’s use has soared by £51m.

The Mayor announced the investigation after learning that the conversion cost had increased from £272m to £323m.

The price of retractable seating, installed to improve the view for football, was one of the main factors behind the cost rise, which triggered Mr Khan’s decision, Sky News reported.

The cost of the seats is said to have risen from an estimated £300,000 to £8m.

Deputy mayor Jules Pipe told Sky News: “Last year the previous administration told the public that the costs had risen in total to around £270m.

“The new Mayor has now been told that cost will be over £320m.

“Understandably, Sadiq has ordered an investigation as to why those two figures are so wildly different.

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“As the new administration at City Hall clearing up the mess of the previous administration, we need to make sure that the stadium runs on a sustainable basis and it is affordable to London.”

The stadium has been beset by problems in recent months after violent clashes broke out between fans at the football venue.

Engineers have said work to move the retractable seating could take 30 days each season – three times as long as the five days initially predicted.

The extra days’ work could threaten planned events, including athletics and concerts, or even delay West Ham’s return for the start of the new football season.

Former mayor Boris Johnson had agreed to West Ham’s request to install the seating as a quick and cost-effective way for the stadium to be converted for athletics and other events.

Mr Pipe said the investigation would look at all aspects of the stadium.

He added that renegotiating the deal with West Ham would be difficult.

The total cost of the stadium is now £752m, which is taxpayer funded besides a £15m contribution from West Ham.

A spokesperson for the Mayor of London said: “The Mayor is deeply concerned about the finances of the Olympic Stadium, which have clearly been left in a total and utter mess by the previous administration at City Hall.

“The former Mayor announced just last year that the total cost for transforming the stadium was £272 million. In reality this is £323 million – a difference of more than £50 million.

“Sadiq has ordered a detailed investigation into the full range of financial issues surrounding the stadium.

“We remain committed to the future of the stadium as a venue for football and other sporting and cultural activities.

“We are confident that London will host a fantastic World Athletics and Para Athletics Championships in 2017.”