NHS 24 now has more than 1,000 staff

Christine Lenihan gave no detailed explanation but she said she was leaving after thinking "long and hard".

Health Minister Andy Kerr ordered a review of the service in February amid concerns about the service including delays in calls being returned.

Ms Lenihan, who was appointed chairman in July 2001, said her four-year term had been a "great privilege".

"NHS 24 now has more than 1,000 clinical and support staff serving the people of Scotland 24 hours every day of the year," she said.

'Huge pleasure'

"It has been a huge pleasure to work with such talented people, and particularly our committed front line staff.

"But there will be changes as NHS 24 continues to improve and evolve further."

She went on: "I have thought long and hard about this and have decided to step aside which, I believe will enable my successor to take forward the next phase of the organisation's development."

Mr Kerr said: "I am very grateful to Christine for all her drive, commitment and energy in building this vital and complex service up from the original concept.

"As a leading Scottish businesswoman, she has made a very important contribution to modernising Scotland's health services."