A City Hall committee has taken the unusual step of using its power of summons to demand that a close aide to the Mayor provides information about the Garden Bridge project.
Conservative members of the London Assembly have been critical of Dame Margaret Hodge's review of the Garden Bridge project, raising concerns about the content of her report as well as the way the probe was carried out.
The review was commissioned by Mayor of London Sadiq Khan.
When Tory AM Andrew Boff pressed the Mayor to release the transcripts and audio recordings of interviews carried out by Dame Margaret, Mr Khan told Mr Boff that he should write to City Hall with a request under the Freedom of Information Act.
Now the assembly's budget & performance committee has taken the rare step of issuing a summons notice to the Mayor of London's chief of staff David Bellamy requesting documents relating to the Garden bridge review.
"Freedom of Information requests and questions to the Mayor at Mayor's Question Time have been dodged and, frankly, we're tired of the obstruction," said Gareth Bacon AM, Conservative chairman of the budget and performance committee.
"The chief of staff needs to supply this information immediately, so we can assess it and decide how relevant it is to our scrutiny of the Margaret Hodge Garden Bridge Review.
"If the Mayor really is as committed to transparency, as he continually says, he will ensure that he and the staff working for him do not seek to stand in the way of the Assembly's legitimate requests for important information.
"The Assembly needs to do its job of scrutinising the issues that matter to London, unhindered."
Whilst the budget & performance committee was holding its meeting on Wednesday morning, Transport for London's board was meeting in another room at City Hall to agree its response to Dame Margaret's Garden Bridge review. The TfL board has accepted all the recommendations.
• The SE1 website make a freedom of information request to the Greater London Authority on 7 July, seeking to obtain several of the transcripts of the interviews carried out by Dame Margaret. At the time of writing, a substantive response has yet to be received.