Belturbet had a charter of 11 James I (1614) establishing a corporation of 12 burgesses and a portreeve with the right to return two MPs. Before 1727 Lord Newtown-Butler had established a dominance over the corporation, although he still did not feel entirely secure. William Conolly (0460) wrote to the Lords Justices' Secretary, Charles Delafaye (0611), who was sitting for Belturbet, on 29 June 1727 that 'Lord Newtown-Butler cannot bring him in for Belturbet borough until he secures a position for his second son hopefully under the care of the Lord Lieutenant.' On 30 September following, Lord Newtown-Butler of necessity returned his son for Belturbet as his brother had brought the family into disrepute with the burgesses. Thus his borough interest was on the wane, and there were those seeking to undermine it by offering freemen £50 for their vote.90 Delafaye was not returned, and Lord Newtown-Butler consolidated his position by returning his sons Humphrey (0317), his heir, the sitting member, and another son, Thomas Butler (0331); when Lord Newtown-Butler, now Viscount Lanesborough, died in March 1735/6, Humphrey returned another brother, Robert (0328), in his place. The next vacancy occurred in December 1753 when Thomas Butler died and Sir John Cramer (0512), Lord Lanesborough's cousin, was returned. By this time the Newtown Act, 21 Geo. II, c. 10, had confirmed the rights of non-resident burgesses and strengthened the position of the patrons of closed boroughs.
The sitting members were returned in 1761,but Edward Tighe (2064) was returned in 1763 following the death of Robert Butler. At least one seat was sold - to Robert Birch (0145) for £2,200 - in 1768 and again in 1776. The Lanesboroughs were impoverished, and between 1776 and 1779 sold Belturbet to David La Touche (1203) for £11,000. In 1781 it returned to the Lanesborough family on the marriage of Elizabeth La Touche to the 3rd Earl of Lanesborough, who made the returns for 1783. In 1782 it was noted that the 'Earl of Lanesborough has the borough of Belturbet - his father sold the borough of Belturbet to Mr La Touche, to whose daughter he himself is married'.91 The Parliamentary List for 1784 states that both seats were sold - more likely one, as the Rt Hon. David La Touche was his father-in-law and the recent owner of the borough. The other MP was Sir Skeffington Smyth (1949). Lord Lanesborough then sold the borough to Lord Belmore (1269) for £8,500 (i.e. £10,500-£12,500 as it included the borough return). Lord Belmore made the returns thereafter, generally for dynastic and political rather than pecuniary reasons, and received the compensation at the Union.