UPDATE: David Edmonds, the chair of Olympic Stadium operators the London Legacy Development Corporation (LLDC), has resigned from his role amid mounting pressure over the spiralling costs of converting the venue into a football ground for West Ham United.

Two days ago the Mayor of London, Sadiq Khan, launched an investigation into the cost of the project, which has risen to around £750m – much higher than originally projected.

Edmonds, who was appointed chair of the LLDC in September 2015, led the board responsible for the Olympic Stadium and played a leading role in planning for and delivering the post-2012 London Olympic Games legacy programme.

The stadium – designed by sports architects Populous – was built for the Games, with a long-term plan in place to reconfigure the ground afterwards to into a multi-purpose arena. In 2015, Khan’s predecessor Boris Johnson said a conversion to make the stadium suitable to host football matches would cost £272m. However, this figure has now risen to £323m.

According to the BBC, unforeseen costs in moving the retractable seating is the main cause of the increased price tag.

As West Ham has signed a deal contributing £2.5m a year in rent and £15m towards the renovations, the shortfall will reportedly be covered by the taxpayer and the LLDC.

In an interview with BBC Radio Four, the chair of the House of Commons Select Committee for Culture, Media & Sport, Damian Collins, said: “These costs seem to be out of control. I think most people would say West Ham have got an unbelievably good deal. Lessons should be learned from this saga.”

A spokesperson for Khan told the BBC: "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.

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

The Olympic Stadium Coalition – a group of 14 supporters’ trusts and groups appealing for greater transparency around the project – called Khan’s enquiry “a breakthrough in our long campaign to highlight the intolerable burden on taxpayers of the rebuilding of the Olympic Stadium to the specification of a well off Premier League football club.”

It predicted the stadium “will operate at a loss for the foreseeable future” and called for the entire deal struck by West Ham, including policing costs, to be examined in the investigation.

The club, which recently issued a five-point security plan in response to persistent crowd trouble at its new home, has not commented on Khan’s investigation.

Responding to the resignation of Edmonds, LLDC chief executive David Goldstone said: "David has made an enormous contribution to the legacy of the London 2012 Games and he has helped to steer the organisation through some extremely challenging issues. We thank him for all his hard work and wish him well in the future."