Queen's County, which he represented until the dissolution in June of that year. He was returned for the borough of Portarlington at the general election in July 1802, but retired from parliament on his appointment as escheator of Munster in December following. At a by-election in February 1806 he was again returned for Queen's County, which he thenceforth continued to represent until the dissolution in December 1832. Parnell was appointed a commissioner of the treasury for Ireland in the ministry of all the talents in February 1806, and took part in the debate on the Irish budget on 7 May following (Parl. Debates, 1st ser. vii. 45–8). He retired from office on Lord Grenville's downfall in March 1807. On 18 April 1809 he brought forward a resolution in favour of assimilating the currency of Ireland with that of Great Britain, which was, however, negatived without a division (ib. 1st ser. xiv. 75–89, 91). On 30 May following his motion for the appointment of a commission to inquire into the manner in which tithes were collected in Ireland was rejected by a majority of seventy-one (ib. 1st ser. xiv. 792–4, 799–80), and on 13 April 1810 he failed to obtain the appointment of a select committee for a similar inquiry (ib. 1st ser. xvi. 658–72). On 19 Feb. 1810 he was appointed a member of the bullion committee, of which Francis Horner [q. v.] was the chairman (Journals of the House of Commons, lxv. 105). He supported Grattan's motion respecting the Roman catholic petitions on 1 June 1810 (Parl. Debates, 1st ser. xvii. 252–6), and on 8 May 1811 made an elaborate speech in defence of the report of the bullion committee (ib. 1st ser. xix. 1020–51). He again brought the question of Irish tithes before the house on 11 June 1811 (ib. 1st ser. xx. 572–80), and in the following session gave his support to Lord Morpeth's motion for an inquiry into the state of Ireland (ib. 1st ser. xxi. 622–35). On the death of his elder brother in July 1812 Parnell succeeded to the baronetcy. On 2 March 1813 he supported Grattan's motion for a committee on the Roman catholic claims (ib. 1st ser. xxiv. 986–1004). As chairman of the select committee appointed to inquire into the corn trade of the United Kingdom, he drew the attention of the house to their report on 15 June 1813 (ib. 1st ser. xxvi. 644–59), and on 5 May 1814 his resolution in favour of permitting the exportation of grain without duty or bounty was carried (ib. 1st ser. xxvii. 666, 707–16, 717, 722). His motion for a committee of the whole house on the laws affecting Roman catholics was defeated on 30 May 1815 by a majority of eighty-one (ib. 1st ser. xxxi. 474–82, 524). On 25 May 1819 he supported Peel's resolutions with respect to the resumption of cash payments (ib. 1st ser. xl. 757–60), and in July following he brought forward a series of forty-seven resolutions concerning the retrenchment of the public expenditure (ib. 1st ser. xl. 1429–38, 1551–3, 1564–8). On 24 June 1823 Parnell asked for the appointment of a committee to inquire ‘into the extent and object of the disturbances existing in Ireland,’ but was only supported by thirty-nine votes (ib. 2nd ser. ix. 1148–85, 1202–3). On 10 Feb. 1825 he opposed the introduction of the Irish Unlawful Societies Bill, and asserted that there could be ‘no other termination to its destructive operation but insurrection and rebellion’ (ib. 2nd ser. xii. 204–33). In the same month he introduced a bill ‘to amend the law in Ireland respecting the subletting of tenements,’ and a bill ‘to regulate the office of justice of the peace in Ireland’ (ib. 2nd ser. xii. 621–4, 624–5). He spoke at great length on the Customs Consolidation Bill on 17 June 1825 (ib. 2nd ser. xiii. 1222–42). On 15 Feb. 1828 he was appointed a member of the select committee on the state of the public income and expenditure of the United Kingdom (Journals of the House of Commons, lxxxiii. 76), of which he was subsequently nominated chairman (Parl. Papers, 1828, vol. v.).
Parnell supported the second reading of the Roman Catholic Relief Bill in March 1829 (Parl. Debates, 2nd ser. xx. 1200–5). On 15 Nov. 1830 his motion for referring the civil list to a select committee (ib. 3rd ser. i. 525–31, 532) was carried against the government by 233 votes to 204, and on the following day the Duke of Wellington resigned. Parnell succeeded Charles Watkin Williams-Wynn as secretary at war in Lord Grey's administration on 4 April 1831, and was sworn a member of the privy council on the 27th of the same month (London Gazette, 1831, i. 643, 874). By entering into an unauthorised negotiation with the French post office, and by encouraging Joseph Hume to bring a motion against our own post office, he exasperated the postmaster-general (the Duke of Richmond), and narrowly escaped dismissal (Greville Memoirs, 1874, 1st ser. ii. 243, n.) The ministry declined to concur in his proposed reduction of the army estimates, which he calculated would save the nation 600,000l. a year (Parl. Debates, 3rd ser. xi. 1020–3), and he was shortly afterwards dismissed from office for his refusal to support the ministry in the division on the Russian-Dutch war question on 26 Jan. 1832 (Thomas Raikes, Journal, 1856, i. 9). Parnell had previously pressed upon