Launceston and Newport, pocket boroughs of the owners of Werrington, and secured the election, as his colleague for Launceston, of Sir George Lee [q.v.], the husband of his step-sister Judith. He secured for Newport, after a contest with the Duke of Bedford's nominees, the return of Sir George's brother, Colonel John Lee, and Edward Bacon, a connection of the Walpoles. Morice at once sought a reward for his electoral successes from his leader, the Duke of Newcastle, and asked, among other things, for a place on the board of green cloth (June 1755). For the moment it was withheld; but Newcastle who, on 23 Oct. 1755, wrote to Morice desiring to see him in order to explain, before parliament met, 'the measures which have been taken for the support of the Rights and Possessions of His Majesty's crown in North America' was reminded of the green cloth promise in the later days of April 1757, when he was trying to form a ministry without Pitt. On 5 May Morice kissed hands on his appointment as one of the clerks-comptrollers of the household of George II ; and a fortnight later he was re-elected for Launceston without opposition. In the winter of 1758, on Sir George Lee's death, Morice declared himself unable to secure the return for Launceston, as Newcastle requested, of Dr. (afterwards Sir Edward) Simpson, Lee's successor as Dean of the Arches. He himself put forward John, second earl Tylney, an Irish peer, in order that he might arrange an accommodation with the Duke of Bedford, with whom Tylney was connected; but Tylney was withdrawn owing to the local unpopularity of the Duke of Bedford, and Morice chose Peter Burrell of Haslemere to represent the constituency. Sir John St. Aubyn, a nephew of Sir William Morice, who had sat for the borough in the previous parliament, was, however, declared by the mayor to be returned by a majority of a single vote fifteen to fourteen. But a petition was immediately presented to the House of Commons, and, owing to Morice's influence with the administration, Burrell was declared duly elected.
Later in 1759 Morice received threatening letters in an endeavour to extort money under peril of being accused of a serious offence. He at once faced the accusers, two of whom were sentenced to be imprisoned for three years in Newgate, and to stand in the pillory in Cheapside and Fleet Street; another accuser fled and the fourth turned informer. The sympathy of the populace was entirely with Morice, but it is evident from his various communications at that time to Newcastle that his health suffered from the consequent worry. In the spring of 1760 he went abroad, and Horace Walpole, with whom Morice had many tastes in common, recommended to the attention of Sir Horace Mann 'Mr. Morrice, Clerk of the Green Cloth, heir of Sir William Morrice, and of vast wealth,' who 'will ere long be at Florence, in his way to Naples for his health.'
Morice was still abroad when, in October 1760, George II died; and, despite the urgent appeal of some friends, his household appointment was not renewed. The Duke of Newcastle was in vain reminded that Morice had spent 20,000l. in support of the administration which had 'turn'd him adrift on the first occasion that offer'd.' Morice took the humiliation quietly; and when his protege, Colonel Lee, M.P. for Newport, was dying, in September 1761, he sent from Naples an offer to place the coming vacancy at the disposal of the government. William de Grey, solicitor-general to the queen, afterwards first Baron Walsingham, was accordingly returned. His accommodating disposition was recognised by Bute, who at once appointed Morice comptroller of the household. He was re-elected for Launceston on 3 Jan. 1763, and seven days later was sworn of the privy council.
Although Bute gave place to George Grenville in the first week of the ensuing April, Morice's tenure of the comptrollership was continued; and he was also appointed lord warden of the stannaries, high steward of the duchy of Cornwall, and rider and master of the forest of Dartmoor. The question was at once raised in the commons, at Morice's own suggestion, whether, by accepting these latter appointments, he vacated his seat; but a motion that the seat was vacant was negatived without a division (19 April 1763), although, owing to his own scruples, his appointment was not formally made out till 28 June. With the fall of the Grenville ministry, in July 1765, Morice's ministerial career approached its end. On 4 Feb. 1771 he was chosen recorder of Launceston, and was sworn on the following 9 Dec. In October 1774, at the general election, there was a struggle against his influence; although he himself was returned for both Launceston and Newport, his power in the former borough was shown to be waning, and in the next year he sold Werrington, and with it the electoral patronage, to Hugh, first duke of Northumberland of the present creation 'a noble purchase,' as was said at the time, 'near 100,000l.' In 1780 Morice retired from parliament; in 1782 he resigned the recordership; and on 20 Nov. 1783 the coalition ministry of North and Fox ousted him from the lord