From 1669 to 1674 Bruce sat in the Scottish Parliament as shire commissioner for Fife, and from 1681 to 1682 as a shire commissioner for Kinross. From April 1685 to May 1686 he reached the peak of his political career, as a member of the Privy Council of Scotland. But, in 1674, he became embroiled in factional rivalry between his patron Lauderdale, and his rivals the Duke of Hamilton and the Earl of Tweeddale. His actions, which apparently included passing information to Hamilton, invoked the fury of the Duchess of Lauderdale, who tried to persuade her husband to deprive Bruce of his offices. Bruce survived, although his relationship with his patron was damaged. Lauderdale described him as "the bitterest factionalist partie man of his quality in all Scotland". This breakdown resulted in Bruce's eventual dismissal as Surveyor General of the King's Works, on the false pretext that Holyroodhouse was finished.