Mayor of London Sadiq Khan has spoken out over his “unhappiness, frustration and anger” at the increasing costs of turning the London Stadium into a multi-use venue.

Built for the English capital’s hosting of the summer Olympic Games in 2012, the stadium is now home to English Premier League football club West Ham United, while also staging athletics and music events.

The initial projected cost of converting the London Stadium for West Ham’s use was £272m (€311.9m/$335.6m), but the eventual cost amounted to £323m.

However, the venue is scheduled to host a number of athletics and music events once the 2016-17 football season has ended, and it is not yet known how much it will cost to convert the stadium for these events, and then back to football for the start of the 2017-18 campaign.

Khan has spoken on a number of occasions of his frustration over the issue and in November ordered an inquiry into the project. This week, he also appointed forensic accountancy firm Moore Stephens to carry out further investigation into the rising costs.

“My unhappiness, frustration and anger is that the cost associated with the original conversion is more than we were promised,” Khan said, according to the Evening Standard newspaper.

“And…the annual cost of turning that into a culture and music venue is more than predicted — to the extent that it looks as if for the foreseeable future we will be subsidising this stadium.

“Had we known the cost would be as much for conversion as it has been, would that have happened? We’ve appointed a firm to find out what happened.

“If it’s going to cost us X million pounds to move it from a football stadium to a cultural one and back again to football, it begs the question: are we getting value for money?”