Douglas was returned unopposed for Dumfries Burghs. His eldest brother Charles, who in 1810 had become 5th Marquess of Queensberry, arranged it with the Duke of Buccleuch.
Douglas’s tendency to follow an independent line was reinforced by the agitation for Scottish burgh reform in the Parliament of 1818. On 23 Mar. 1819 he was a spokesman for the overhaul of burgh financial administration and urged that the experiment at Montrose should be extended to Aberdeen. He supported the lord advocate’s bill on the subject, 26 Apr., and on 6 May he advocated and voted for a committee of inquiry into the burghs and was placed on it. As a member of the Camelford election committee, he was in the minority against the issue of a new writ until the committee’s report had been analysed, 8 Apr. On 18 May, however, he was in the government majority against Tierney’s censure motion. Then on 14 June he joined the minority on the cash payments bill. On 21 and 27 Dec. 1819 he favoured inquiry into distress in the manufacturing districts and in the trades both in Scotland and throughout the country. Douglas died 5 Dec. 1859.
