The professional body for more than 400 of Scotland's top legal figures confirmed yesterday that Mr Darling had before Christmas resigned his membership after 25 years.
It came as reports suggested the faculty had launched a conduct investigation into his behaviour in relation to the expenses scandal that engulfed politicians during 2009.
The body, which regulates the conduct of Scotland's 460 advocates, was said to have received a complaint about Mr Darling's behaviour after he was found to have paid for an accountant's advice on his tax return with taxpayers' money as well as "flipping" his second home four times in a period of five years.
He also repaid 700 of "service charges" relating to his London flat after conceding he had made a mistake in claiming for them.
The organisation's code of conduct states that any member should not bring the faculty into disrepute.
A spokeswoman for the Chancellor, who qualified as an advocate in 1984, insisted that his departure from the faculty was coincidental.