Jim Sheridan had adhered to the party line throughout his five years as a Labour MP.
Jim Sheridan had been a staunch supporter of Tony Blair
The MP for Paisley and Renfrewshire North had backed the government on a number of divisive issues, including the war in Iraq and 90-day detention for terror suspects.
One fellow MP even described him as being "largely anonymous" at the House of Commons.
However, on Wednesday he became the first MP to resign a post over the UK Government's stance on the Middle East conflict when he quit as parliamentary private secretary to the defence team.
The lifelong Labour and union activist began his Westminster career by winning the safe West Renfrewshire seat at the 2001 general election.
Prior to this, Mr Sheridan had spent most of his adult life in the manufacturing industry.
The 52-year-old worked as a material handler for defence contractor Thales Optronics and also served as a convenor for the Transport and General Workers Union.
Mr Sheridan's political career started in 1999 when he was selected to fight the Erskine Central ward on Renfrewshire Council, which he won after a fierce contest with the SNP.
Within a year the married father-of-two was fighting for a seat at Westminster.
He gained 47% of the vote in West Renfrewshire and won with a majority of more than 8,000.
Following boundary changes in 2005, Mr Sheridan went on to fight Paisley and Renfrewshire North, where he increased his majority by about 3,000.
His personal campaigns included payouts for dock workers affected by asbestos-related diseases, and a successful private member's bill that tackled illegal gangmasters.
Mr Sheridan made minor headlines in 2004 when he was found to have claimed the sixth highest sum of expenses at Westminster.
At the time he sat on three parliamentary committees and was commuting from Erskine.