A former head of the SAS has quit the armed forces amid speculation he was unhappy with resources.

Brigadier Ed Butler, one of the UK's most experienced and decorated special forces soldiers, led British troops in Afghanistan as commander of 16 Air Assault Brigade.

In a statement, Brig Butler said that he was resigning his commission in order to spend more time with his family and take up opportunities in the commercial sector.

It is understood that he was recently passed over for the post of director of special forces.

Paying tribute to the servicemen and women he fought with in Iraq, Afghanistan, Northern Ireland and the Balkans, Brig Butler said that they operated "within the well-known constraints and restraints", leading to speculation that his departure was motivated by concern over troops' equipment and conditions.

But sources within the Ministry of Defence insisted that Brig Butler did not intend his comments to be seen as a "protest vote".

In his statement, Brig Butler said: "I have had an incredible two dozen years in the Army and have been so privileged to lead some extraordinarily brave men and women, from all three services, on hugely challenging operations from Northern Ireland to the Balkans, Iraq, Africa and Afghanistan.

"Their resourcefulness, commitment and ability to continually deliver operational success, within the well known constraints and restraints, is both remarkable and humbling. We owe them a huge debt of gratitude.

"It is now time to move on to new challenges and rewards, transferring all the skills and experiences I have learnt in the military into the commercial sector. Most importantly I can now spend more time with my young family."

© Independent Television News Limited 2008. All rights reserved.