ASCO Group, the Scottish oil field logistics specialist, has announced the sudden exit of chief executive Derek Smith and long-standing chairman Billy Allan.

ASCO Group, the Scottish oil field logistics specialist, has announced the sudden exit of chief executive Derek Smith and long-standing chairman Billy Allan.

Mr Smith, who has worked for the company since 2007, has been replaced by Alan Brown, most recently chief executive of Rentokil Initial.

The firm said an announcement will be made on Mr Allan's replacement "in due course".

Aberdeen-based ASCO, owned by private equity house Doughty Hanson and its management, did not elaborate on the reasons behind the departures, beyond stating that Mr Smith had left to "pursue other opportunities".

ASCO, which employees more than 2000 staff in 35 locations across the world, credited with Mr Smith with being closely involved with the "substantial growth" it has seen in recent years.

It noted ASCO had won a number of "ground breaking" contracts during his tenure, including its multi-year Tanzanian supply base support contract.

Meanwhile it said Mr Allan, who sits on the board of Partick Thistle Football Club, has indicated to step down from the business. He was credited by ASCO with transforming the fortunes of the company when he was appointed chief executive in 2006.

ACOS said Mr Brown brings extensive experience in establishing and running global organisation to the chief executive role.

He spent five years as chief executive of Rentokil Initial until October last year, and before than spent 25 years at Unilever. His time with the conglomerate saw him hold various roles in the UK and Europe, before becoming chief executive of its operations in firstly Taiwan and then China.

After leaving Unilever he returned to the UK and took up the post of chief financial officer at Imperial Chemical Industries, and played a lead role in the sale of the business.

Mr Brown said: "ASCO has an enviable reputation for providing high levels of service to its clients and supporting the development of their businesses. I aim to build on this reputation by extending both the range and geographic reach of ASCO's services."

"With its roots in Aberdeen, ASCO has become an international business with a strong brand built on a strong service ethos. I would like to thank my predecessors, Derek Smith and Billy Allan, for their significant contribution to developing this platform, on which we will continue to build."

In the last three years ASCO has shift its focus from the North Sea to energy projects across the globe, supporting major oil companies with operations in the Middle East, Africa, Australia and North America.

In May it announced it became the majority shareholder in an Australian logistics business, Bonnie Rock Transport, for £15 million as part of its international expansion plans. It revealed it had secured £25m of bank funding for further acquisitions.

The most recent accounts for the business show that it grew turnover by 13.3 per cent to £768.6m in the year ended December 31, with operating profit rising to £14.8m from £5.7m.