A senior ESB executive who was unsuccessful in the recent competition for the post of chief executive has resigned.

Mr Dónal Curtin, director of international investments at the State company, will leave in July.

Mr Curtin (54) was one of two internal candidates in the final shake-out of the race to succeed Mr Ken O'Hara. He was seen by certain senior observers as the favourite.

His internal rival, Mr Padraig McManus, was appointed at a board meeting in February after a special sub-committee failed to agree on a preferred candidate. Two external candidates were also on the shortlist.

Mr Curtin was not in the State yesterday. Staff were informed of his departure on Monday.

A source said: "Dónal feels it is time to pursue other opportunities both at home and abroad."

The ESB chairman, Mr Tadhg O'Donoghue, said the company regretted losing Mr Curtin.

The board was informed of his resignation at a special meeting on Saturday, which was called to initiate a refinement of the ESB's overall business strategy.

Mr O'Donoghue said: "Obviously, we didn't particularly want him to go but he thought he had done his service here.

"He came to me and he asked me if he could leave the company. We tossed it around and I made it clear to him that we didn't want him to go."

When it was suggested that Mr Curtin ranked among most able figures in the ESB, Mr O'Donoghue said: "Very, very, and that was one of the reasons that I wasn't anxious to see him go."

Mr Curtin is seen as an entrepreneurial and experienced figure in the ESB. He joined the company in 1970 after studying engineering at UCC.

He has worked with the company's international division since the early 1980s after a period at the networks and distribution end of the business.

Mr Curtin was a key figure in the biggest initiatives undertaken by the ESB's international division.

These include a gas-fired plant at Coolkeeragh, Co Derry, and an 800 megawatt power station in the Basque region of Spain. Both these projects are nearing completion.

Mr O'Donoghue said: "We wanted him to stay on and complete the big projects he was involved in in Northern Ireland and in Spain."

Last year, Mr Curtin led an initiative to invest €1.8 billion purchasing a cluster of eight power supply companies in Poland.

The ESB was believed to be among the favourites, but the Government forced the company to withdraw from the competition within hours of the deadline for a binding bid.

It was a serious setback for the ESB but the Government said it was the scale of the project - not its quality - that led to its rejection of the plan.

Mr Curtin was involved in the development of Britain's first combined cycle gas turbine generation plant at Corby, Northamptonshire, which is part-owned by the ESB.

Other projects run by the division include facilities management contracts in Malaysia, Dubai, the Lebanon and Ghana.