Scotland's largest transport authority has been hit by a third resignation amid an ongoing row over expenses.
South Lanarkshire Labour councillor Davie McLachlan stepped down as vice chair of Strathclyde Partnership for Transport (SPT) on Thursday.
He follows Ron Culley who resigned earlier as chief executive, and Glasgow Labour councillor Alistair Watson who stepped down as chairman on Monday.
Financial watchdog Audit Scotland is to investigate expense claims at SPT.
The row which led to the resignations flared after expense claims from SPT officials were reported following a Freedom of Information request.
It emerged that senior figures in the organisation claimed more than £100,000 between 2006 and 2009.
There have also been questions about expense claims from officials in Manchester on the day of the Uefa Cup final in 2008 between Rangers and Zenit St Petersburg, which the Ibrox side lost 2-0.
SPT has since asked its external auditors, KPMG, to review its expenses policy.
Announcing his resignation on Thursday, Councillor McLachlan said: "I have today reluctantly decided to step down from the position of vice chairman of the Strathclyde Partnership for Transport.
"I do so for what I believe is in the best interests of SPT.
"Over the past few days SPT has received unjust criticism which has reflected on me. I believe that my position will be vindicated once the KPMG report is published."
Earlier, Ron Culley stood down as chief executive of the transport body.
Mr Culley, who has been on sick leave since January, is understood to be seeking early retirement on the grounds of failing health.
In a statement, Mr Culley said: "I'm fortunate to have enjoyed a career in public service which has permitted me to serve the city I love at the highest levels.
"I am entirely confident that the investigation being undertaken under the auspices of Audit Scotland will exonerate officers of SPT as all delegations over the past four years were approved in advance by an authority comprising members of every major political party.
"Lessons learned were reported back to the authority and have or are being implemented.
"That notwithstanding, my present health problems do not currently permit me to bring the energy levels to bear on the work necessary to drive the authority forward and to serve the needs of our new chairman as he would require.
"I have been privileged to work within a team of excellent public servants as well as members of the authority who are dedicated to serving the travelling public."
On Wednesday, it emerged that Glasgow councillor Jonathan Findlay is set to take over the role of chairman at SPT after Councillor Watson stood down on health grounds.
Mr Findlay, who works as a lawyer at East Dunbartonshire Council, has been urged by Glasgow City Council leader Steven Purcell "to take a firm grip of SPT and get to the bottom of everything that is going on there".
His appointment as chairman is likely to be confirmed at a SPT board meeting on 26 February.