Collins, Thomas (d. 1814), linen merchant and informer, was established in Dublin by 1769, when, a member of the merchants’ guild, he was admitted as a freeman. He belonged also to a businessmen's society called the Aldermen of Skinner's Alley, which was traditionally conservative though by the early 1790s some of its members were liberals. At one time a man of substance, with landed property in King's Co. as well as a linen and silk business in Capel Street and house property elsewhere in Dublin, Collins went bankrupt early in 1790.
At the formation of the radical Society of United Irishmen (9 November 1791) Collins joined, then promptly approached John Giffard (qv), a leader of the government interest in Dublin municipal affairs, with an offer to report on its proceedings. From then until the dissolution of the society in May 1794 he secretly sent regular reports to Giffard, who passed them on to the under-secretary, Edward Cooke (qv). They were ‘models of their kind – clear, regular, well arranged’ (McDowell, ‘Personnel’, 13). Often they were accompanied by Collins's own summons to the meeting on which he was reporting; the summonses were important because they contained names and addresses of candidates for membership. Over 360 names of men admitted to membership are listed in McDowell's prosopography (1940). The Dublin Society of United Irishmen was dissolved by a warrant based on information supplied by Collins, who was the first of many government informers on what became a revolutionary and subversive organisation.
Cooke then sought a post in the West Indies for Collins, who had interspersed his letters with complaints of impecuniousness. In 1796 Collins was in London. In 1797, imprisoned for debt, he complained of having received only £845 for his services to the Irish government since 1791. In 1798 he was appointed a naval officer in Dominica, a position worth £600 p.a. He finally arrived in the colony early in 1800. He died there in the first half of 1814. It appears that in 1770 he married Susanna North who brought him a dowry of £600.