Glass panels at City Hall, the headquarters of the Greater London Authority near Tower Bridge, have started cracking two years after it was completed, leading the GLA to call for an explanation from suppliers,

Several floor-to-ceiling glazed partitions at the building, which was designed by Foster and Partners, have cracked over the past few months. The GLA is holding talks over the question.

A GLA spokesperson refused to name the glass supplier but confirmed that the company was investigating the matter. He said: “Although we are awaiting final results, it seems likely to be a glass manufacturing fault due to nickel sulphide inclusions. We are working with the glass manufacturers to ascertain if this is the case.”

The spokesperson said the damaged glass would need replacing but emphasised that the GLA would not assign a supplier until it had seen the outcome of its inquiry. He said: “We will want those panels replaced as soon as possible. But until the report is complete we really cannot say who will be undertaking the work.”

The damage is the latest in a series of problems to beset the £43m building.

A group of London assembly members were trapped in one of the building’s innovative lifts earlier this autumn and the building also had to be evacuated recently when a window cleaner’s crane crashed into the glass exterior.

Bob Neill, the Tory leader on the assembly, said: “Not a week goes by without repairs. None of this is helped by the fact that a building designed to house 420 staff is now stuffed with almost 700.”

City Hall was widely hailed as an example of bold architecture when it opened two years ago. However, critics warned it might prove to be impractical.