Former Scottish Secretary Des Browne today pledged loyalty to the Prime Minister as he prepared for life on the backbenches.
Mr Browne, 56, who was replaced by Jim Murphy in today's reshuffle, said he told Gordon Brown "some months ago" that he intended to step down from the Government next spring.
"Therefore I fully understand why he has made the decisions that he has in this reshuffle," Mr Browne said.
"It has been a privilege to serve this Labour Government in all six of the ministerial jobs that I have held over the last seven years."
He went on: "I am proud of what I have achieved as Scotland's voice in the Cabinet and in renewing the relevance of the Scotland Office."
He cited legislation giving legal protection for Scotch whisky and establishing the Calman Commission on devolution as examples of the "real benefits" delivered for Scotland.
"I am a strong and loyal supporter of our Prime Minister Gordon Brown, and of his Government," he said.
"From the backbenches and in my constituency of Kilmarnock and Loudoun I will continue to work hard to pursue our agenda of social justice and to secure a fourth term for Labour."
Mr Browne's successor moves to the Scotland Office from the post of Minister for Europe.
Mr Murphy, 41, entered Parliament in the Labour landslide of 1997, where he captured Eastwood - up to then, the Tories' safest seat in Scotland.
The SNP spoke derisively of "a thoroughly botched reshuffle".
SNP Westminster leader Angus Robertson said: "Since Alex Salmond became First Minister, he is on his third Labour leader in the Scottish Parliament and third Secretary of State.
"And it seems that Jim Murphy was second choice as Scottish Secretary."
Mr Robertson went on: "Des Browne's departure shows just how much of a dog's dinner Gordon Brown has made of his reshuffle.
"Hard on the heels of David Cairns' resignation from the Scotland Office, Des Browne's exit shows that right through the Scotland Office tea
And Tories mocked Mr Brown over his "no time for novices" message at the Labour Party conference.
Shadow Scottish secretary David Mundell said: "I believe that the fact that the two Scotland Office ministers have found themselves, in as many weeks, unable to continue in Gordon Brown's Government reflects the widespread doubts that exist even within the Labour Party about his leadership.
"Staggeringly, the complete opposite of Mr Brown's quip that this 'is no time for novices' now seems to apply to his Scotland Office."
Tavish Scott, leader of the Scottish Liberal Democrats, said: "Will Jim Murphy be brave enough to recognise the need for home rule and back Liberal Democrat calls for the Scottish Parliament to have responsibility for raising its own money?"
He also challenged Mr Murphy to accept the principle that Scotland should continue to receive council tax benefit if that tax is replaced by a local income tax.
CBI Scotland director Iain McMillan welcomed Mr Murphy's appointment.
"We look forward to working with him on the many issues which affect Scottish business that are the responsibility of the UK Government," he said.
"We also welcome the fact that Scotland will once again have a full-time voice within the UK Cabinet."
Mr Murphy's appointment means Scotland will have a dedicated voice in the Cabinet for the first time since 2003, his office said.
Mr Murphy said: "As Scotland's man in the cabinet I will represent the interests of Scotland at all times."
Born in Glasgow, his family emigrated to South Africa but he returned to Scotland at 18 to study at Strathclyde University.
He chaired the National Union of Students at UK level and in Scotland.
His first appointment to ministerial rank came after the 2005 election when he went to the Cabinet Office and a year later became employment and welfare reform minister of state.
Last year he was appointed Europe minister of state.
He said tonight he was determined to build on the Scotland Office's role as "guardian of the devolution settlement".
"We are at a pivotal point in Scotland's history and the return to a dedicated Scottish Secretary role underlines both the Prime Minister and UK Government's commitment to Scotland's future," he said.
