Former Taoiseach Brian Cowen and former AIB chief executive Colm Doherty are among six people to be appointed to the board of fuel supply chain Topaz Energy Group.

Businessman Denis O’Brien has also been appointed a non-executive director at the firm along with Sean Corkery, chairman and CEO of SiteServ, which Mr O'Brien bought last year.

Lucy Gaffney, who is chairperson of Mr O’Brien’s Communicorp Group, and Emmet O’Neill; co-founder of Smiles Dental make up the six new appointments announced today.

Mr O’Brien recently took control of Topaz after acquiring around €304 million of the group’s loans from the Irish Banking Resolution Corporation.

The company said that its chief financial officer - Niall Devereux, has also been appointed to the board.

Topaz chairman John Callaghan said the new directors would “bring a unique level of expertise and knowledge which will be invaluable in the continued growth and expansion of Topaz.”

Topaz operates 330 fuel stations across Ireland and currently employs around 1,700 people.

In the year to March 2013 it recorded revenues of €3.17bn, with an operating profit of €296,000.

However, interest costs on the company’s debt saw it report a loss after tax of €13m.