Leighton Holdings announced Wednesday the sudden resignation of board chairman David Mortimer, effective immediately.

An independent non-executive director since 1997, Mortimer was elected chairman of Leighton in June 2007. Australia's largest construction group by revenue said he was leaving for personal reasons.

“Whilst the last 12 months have been very demanding, I am pleased to be leaving after the board has addressed legacy issues and has been able to announce a positive forward outlook for the company. I wish the Leighton Group well in its future endeavours,” said Mortimer.

Mortimer dealt with a number of challenges including the transition to a new chief executive officer, the takeover of Leighton’s major shareholder and the April 2011 profit downgrade and subsequent capital raising.

“The board of Leighton thanked Mr Mortimer for his great contribution to the company over the last 14 years and wishes him well in the future,” Leighton said.

A successor is expected to be announced in the near future.

The resignation caught the market in surprise, with the Leighton shares down 80 cents, or 3.6 per cent, to $21.20 in afternoon trade after rising as high as $22.48 earlier Wednesday.