A mayoral advisor embroiled in a row over City Hall expenses has resigned from his post.
Ian Clement, deputy mayor for external relations, admitted he made a "crass mistake" after he ran up about £2,300 on a corporate credit card.
Further discrepancies have now emerged in the use of expenses when Mr Clement was leader of Bexley council.
London's mayor Boris Johnson said he was "extremely angry" and described Mr Clement's position as "untenable".
'Let you down'
Initially the mayor had supported Mr Clement, saying his behaviour did not amount to dishonesty or deception.
However, further revelations of Mr Clement's use of his corporate credit card forced him to quit his post.
In his resignation letter, Mr Clement said: "It has been a pleasure to work for you and I am sorry that I have let you down and deflected away from the excellent work you and indeed your team are doing in delivering for Londoners."
Mr Clement's resignation cannot be considered an end to the matter
Last week, it emerged that Mr Clement had bought groceries and paid for meals out on his corporate credit card.
Personal use of a corporate credit card is a breach of City Hall regulations.
In a letter to Mr Clement, Mr Johnson said: "I was extremely angry at the liberties you took with your corporate credit card, but last week I made the essential distinction between behaviour that is crass and anything that amounts to dishonesty or deception.
"In the light of the further discrepancies in your expenses that have emerged this morning, it is clear to both of us that your position is untenable."
Mr Johnson has lost two deputy mayors and two senior advisors.
Among them was Ray Lewis who resigned as deputy mayor for youth in July amid claims of financial irregularities.
Jennette Arnold, chairwoman of the London Assembly's business management and administration committee, said the latest case raised serious issues.
The Labour assembly member said: "Mr Clement's resignation cannot be considered an end to the matter.
"Serious questions remain about how long the misuse of the card continued, apparently undetected, and the type of expenditure charged to the GLA."
The case will be discussed at a meeting on Wednesday, when assembly members will question Mr Johnson's chief of staff, Sir Simon Milton.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.