West Ham United are involved in a legal dispute with their London Stadium landlords over plans to install 3,000 new seats.
The Hammers, who are the lead tenants of the former Olympic Stadium on a £2.5m-per-year lease for 99 years, want to increase its capacity from 57,000 to 60,000 and then 66,000.
However, the London Legacy Development Corporation – which runs the ground – has issues with the running costs.
Gerry Murphy, the acting chief executive of the LLDC, told the London Assembly on Wednesday: "There is a dispute with West Ham about what the contract says in terms of capacity.
"West Ham have absolutely said that they want to increase the capacity to 60,000. And actually they want to further increase the capacity to 66,000.
"LLDC and E20 (the landlords) disagrees with their interpretation of the contract. We feel that actually if West Ham want to enjoy more seats then they should commensurately pay more.
"And that's the gist of the disagreement between us and it is subject to legal proceedings."
A West Ham spokesperson said in a statement issued to PA: "These seats are in London Stadium already, have always been there, and have already been paid for under the terms of our concession agreement.
"Having sought a resolution of this matter for many months, West Ham United are seeking a legal declaration."
Wednesday's meeting followed the publication of the Moore Stephens Olympic Stadium Review.
