The financial details of West Ham's move to the Olympic Stadium should be made public, the Information Commissioner has ruled.
The London Legacy Development Corporation (LLDC) -- set up to ensure the long-term success of the London 2012 site -- and West Ham have insisted the deal involving the largely taxpayer-funded stadium should remain private for reasons of commercial confidentiality.
At the start of this month the Government rejected a request from a host of supporters' clubs for an inquiry into West Ham's move to the 54,000-capacity stadium.
The Hammers will take on a 99-year deal as anchor tenants starting from next season but the decision to hand West Ham the keys to the stadium has been questioned since it was first announced two and a half years ago.
A BBC documentary aired last month detailed figures it claimed West Ham would be saving due to the agreement with the LLDC.
Since then, eight supporters' groups started a petition for an inquiry into the details of the decision -- and they have now won the backing of the Information Commissioner.
"We are disappointed by the Information Commissioner's decision which we believe will damage our ability to secure the best deal for the taxpayer in future," said an LLDC spokesperson.
"The stadium will have many users and publishing the contractual details will undermine our ability to deliver the best financial outcome from numerous future negotiations.
"We always strive to balance transparency while protecting the taxpayers' financial interest and we are considering the ruling carefully as we decide what action to take."
West Ham, in a statement on Wednesday afternoon, said they supported Johnson's stance that their move from Upton Park provides a sustainable future for the Olympic Stadium.
But the Premier League club challenged Johnson's comments suggesting the financial terms of the deal should be made public and endorsed the LLDC's view that doing so would damage the taxpayer in future.
"West Ham United shares the Mayor's view that our presence at the former Olympic Stadium guarantees it a viable and sustainable future," said a club spokesman. "Our 99-year agreement will not only return hundreds of millions of pounds to the taxpayer, it will also ensure that London's Olympic Stadium will not join the long list of other former Olympic Stadiums that are rotting away through lack of use.
"The LLDC have stated their disappointment at the Information Commissioner's Office ruling as they believe it will damage their ability to secure the best deal for the taxpayer in future and we share those sentiments.
"The club would like to point out, so that everyone is 100 percent clear, that it is not party to the Freedom of Information Act, and that the Information Commissioner's Office ruling is not against West Ham United, it is against the LLDC.
"The club is now working with the LLDC to decide the appropriate next step."
West Ham, who have played at their current Upton Park home since 1904, will host all of their home matches at an Olympic Stadium sporting the club's livery and colours. British Athletics also has a deal to take control of the arena for one month every summer.
The Anniversary Games and the 2017 World Athletics Championships are set to be hosted there, but West Ham have had to face criticism, with a familiar complaint being that a football club playing in the richest league in the world should not receive taxpayers' subsidy for a new home.
It has been reported that the annual rental agreement on the 99-year lease is around £2.5 million.
A coalition of club supporters' trusts, formed to campaign on the issue, will call on London Mayor Boris Johnson not to appeal against the decision and to publish the contract. West Ham could also appeal against the ruling from the Information Commissioner's Office.
"The Information Commissioner's decision could not have been clearer, and it is equally clear to us that publication must follow," said a statement from the coalition.
"This campaign is publicly backed by 25,000 individuals, football supporters' trusts from around the country, and the public interest in the issue is there for all to see.
"We call on the mayor not to use the appeal system to delay publication of this document further. If he does it will open him up to the suspicion that he has something to hide."