London mayor Sadiq Khan has ordered an investigation into a £50m increase in the cost of converting the Olympic Stadium into the home of West Ham United.
The London Stadium conversion was expected to cost £272m, but the figure has now risen to £323m.
Premier League side West Ham moved into the stadium at the start of this football season.
A spokesperson for the London mayor 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.
“Sadiq has ordered a detailed investigation into the full range of financial issues surrounding the stadium.”
Labour London assembly member Andrew Dismore pointed the finger of blame at the former mayor, Boris Johnson:
This is a staggering burden to place on taxpayers. It's only a year ago that Boris Johnson promised both full transparency and that no more public money would be spent on this project. Londoners must now add the stupendous costs of retracting the seating to the other numerous poor deals for the taxpayer the West Ham contract contains. This is yet another case of the former Mayor taking his eye of the ball and failing to scrutinise or appreciate the detail of the West Ham deal.