The brother-and-sister team that set up Stagecoach is vacating the driving seat after the transport group showed declining revenues.

Sir Brian Souter, 65, will step down as chairman but stay on the board, while Dame Ann Gloag will retire from the board completely, the company announced.

The siblings helped grow the business into what is now claimed to be Britain’s biggest bus, coach and tram operator, employing 24,000 people across the country and with a fleet of more than 8,300 vehicles.

Sir Brian said: “At the age of 65, the time is right for me to step down as Stagecoach chairman to spend time on my other interests and with my family, including my three young grandchildren.”

He and his sister started with a handful of second-hand buses in 1980, running inter-city services in Scotland, according to his official website.

Dame Ann and her husband, Robin, bought a school bus, while Sir Brian used his father’s redundancy money to buy two coaches.

The company was given a boost in 1985 when the Thatcher government deregulated all bus services outside London.

Sir Brian added: “My family and I continue to have a significant shareholding in Stagecoach and I have every confidence in the management team, our strategy and the positive prospects of the business.

“I look forward to continuing to represent the interests of stakeholders as a non-executive director on the board.”

John Moore, at investment management firm Brewin Dolphin, said the pair “have made invaluable contributions not only to Stagecoach as an individual company, but Scotland’s entrepreneurial and business community”.

The announcement comes as figures showed revenue has dropped significantly as Stagecoach has scaled back over the last 18 months – from more than £1 billion in the first half of last year to £800 million in the most recent six-month period.

Pre-tax profit was up 35% to £65.9 million; however, on an adjusted basis it fell by £6.5 million to £66.6 million.

Chief executive Martin Griffiths said: “Our updated strategy is based on three key objectives: maximise our core business potential, manage change through our people and technology, and grow by diversifying.”

Mr Moore, from Brewin Dolphin, said: “While this has hit revenues and transformation programmes are almost invariably complex, the moves seem to be a step in the right direction given the wider transport environment.”

Mr Griffiths said the company could soon benefit from a new national bus strategy which the Government has committed to.

“Whatever the result of the General Election, there is a real opportunity to leverage the potential of the bus to support economic growth and improved connectivity in our communities, as well as addressing the major challenges of road congestion and air quality which blight our biggest towns and cities,” he added.

August Graham is PA City Reporter.