London Mayor Sadiq Khan's investigation into the spiralling costs of converting the London Stadium into a football ground has received approval from fan and taxpayer groups.
A "deeply concerned" Khan has ordered a probe into how the conversion of the 2012 Olympic venue has risen from an expected £272m last year to £323m, requiring taxpayers to fork out an additional £50m.
When West Ham first signed a tenancy deal in 2013, the conversion cost was stipulated to be just £154m
West Ham themselves contributed £15m to the refitting bill and are renting the stadium at a current rate of £2.5m per season.
Yet a number of furnishings required to host football at the stadium, such as corner flags, pitch maintenance and the goalposts will fall on the taxpayer.
A coalition of 14 different football fans' groups and trusts welcomed Khan's investigation and said full details of the conversion costs should be made available to the taxpayer who would be contributing to the bill.
"This is a breakthrough in or 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," said the group in a statement.
"We have never objected to the idea of West Ham playing at the stadium; the question is simply one of how much the club should pay, and how much the taxpayer should be expected to fund.
"Only this week, we have learnt that the naming rights deal for the stadium has fallen through. As a result we believe this means the stadium will operate at a loss for the foreseeable future, especially if the police seek to recharge the costs of their increased presence at the stadium due to crowd control issues.
"The entire deal and not just the rebuild costs should be examined in detail, by the Mayor and the taxpayer."
The London Stadium's reputation has plummeted since West Ham moved into the stadium at the beginning of this season following numerous reports of fan disorder inside the ground.
Yet when it comes to the costs of the stadium, the TaxPayers' Alliance chief executive said ire should be saved for those in City Hall who allowed the deal to go ahead.
"For too long the details of this shabby deal were kept in secret and lacked proper scrutiny so Sadiq Khan is absolutely right to look again at the case," said O'Connell.
"But instead of focusing our anger on West Ham for taking advantage of this ludicrously generous taxpayer funded subsidy, we should instead be demanding explanations from those that signed off on this agreement and ask how they ever thought that this offered value to those of us footing the bill.
"It's now down to those in charge of the inquiry to get to the bottom of how West Ham were gifted the deal of the century while ensuring their investigation doesn't end up costing the taxpayer as much as the stadium."