At Eton Frere was a friend of Canning, with whom he contributed to the Microcosm (1786-7) and who promoted his public career. Canning, who endeavoured to get him a post at the Foreign Office through Pitt, wrote on 17 May 1796 that Frere was coming into Parliament ‘at a very easy price, for a very easy seat in a Cornish borough’.
On 1 Apr. 1799 he succeeded Canning as under-secretary of state at the Foreign Office by previous arrangement. He proved to be one of the least efficient men of business the department had ever known, ‘distrait and poetical, and in lieu of writing a dispatch may be tempted to write a sonnet’. Lord Grenville his chief, who complained to the King of Canning’s having recommended Frere, freed himself from ‘inconveniences and anxieties’ by sending him to Lisbon in October 1800 as minister. George Rose remarked that Frere was ‘the third gentleman who has had a large or a forced provision for himself to induce him to give up the situation of under-secretary to his lordship on account of insufficiency’. He had retained his seat, but Canning advised him, 7 Nov. 1801, not to seek re-election at the dissolution: ‘it would not be worth your while’. ‘I am clear’, he added a fortnight later, ‘that you are much the best out of it.’ When Pitt asked Canning whether Frere was interested in coming in again for Looe ‘on the same terms as before’ (£2,000) in December, Canning felt justified in telling him that he thought not: so he reported back to Frere on 14 Dec.
Frere was transferred in September 1802 to Madrid, where the meddling of his mistress Lady Erroll in Court politics did him no good. He returned home in 1804, after a quarrel with Godoy, the Prince of Peace, with a pension of £1,700 a year and a place on the Privy Council. When Canning was negotiating with Lord Grenville in February 1807, the latter was prepared to bring him into office with Canning but, by Frere’s account, Lord Holland vetoed it. On becoming Foreign secretary under Portland in 1807, Canning wished to provide a place for him, but found it difficult, as Frere wanted the woods and forests: this would necessitate his being in Parliament and during his father’s lifetime he lacked the means, he admitted, to provide himself with a seat. Canning urged Lord Lonsdale, 27 Apr. 1807, to supply him with one, only to discover that his pension, being in excess of £1,200 a year, disqualified him from sitting in Parliament. On 10 May 1807 the King, on Canning’s recommendation, agreed to his appointment as minister to Prussia, which would extinguish the pension, and thus make him eligible for a seat. Lonsdale was willing to find one for him, but Canning nominated someone else for the seat, 14 May. In the meantime the continental situation was such that Frere never set out for Berlin. Instead, he returned to Madrid in October 1808 but, still ‘terribly unfit for his situation’, was recalled within a year, after being blamed for the retreat to Corunna. Canning and he soon drifted apart.
Having succeeded his father to £2,000 p.a., he left public life and devoted himself to literature. Lord Holland was not alone in considering him a man ‘of a warm and generous disposition, of singular and original wit, and of great literary accomplishments’, and blamed Canning’s judgment for Frere’s curious venture into diplomacy: ‘his artless temper, his ill-directed suspicions, his absence, occasional rudeness, and habitual indolence and singularity, all obviously disqualified him for that line’. Later he refused the St. Petersburg embassy and twice declined a peerage. After 1818, because of his wife’s melancholia, he resided in Malta, where he died 7 Jan. 1846.