Member of Parliament

Lambton first stood for Parliament at the 1945 general election in the safe Labour seat of Chester-le-Street, then Bishop Auckland in 1950. He was elected to Durham City Council and to Durham County Council in 1947, serving for two years. He was elected Member of Parliament for Berwick-upon-Tweed in 1951, where he served until 1973.

Under-Secretary of State

In 1970, Lambton was made a Parliamentary Under-Secretary of State for Defence (RAF). He succeeded to the Earldom of Durham upon his father's death on 4 February 1970 but disclaimed it on 23 February to continue as an MP and Government Minister. He nonetheless insisted on being addressed as 'Lord Lambton', the form of address appropriate to his former courtesy title. However, a ruling of the Committee for Privileges said that he should not do so in the House of Commons, since he had renounced his peerage titles. Contradictory rulings from two Speakers, Horace King and Selwyn Lloyd, then left the point unresolved.^[6]

Resignation

In 1973, Lambton's liaisons with prostitutes were revealed in the Sunday tabloid The News of the World. The husband of one of the prostitutes, Norma Levy, had secretly taken photographs of Lambton in bed with Levy and had attempted to sell the photographs to Fleet Street tabloids.^[7] As well, a police search of Lambton's home found a small amount of cannabis. On 22 May, Lambton resigned from both his office and Parliament; this caused a by-election for his seat which was won by Alan Beith for the Liberal Party. Shortly after, the name Jellicoe emerged in connection to a rendezvous for one of Norma's girls at a Somers Town mansion block which had been named Jellicoe House, after the earl's kinsman Basil Jellicoe (1899–1935), the housing reformer and priest from Magdalen College (Oxford). There was a confusion and Lord Jellicoe, the Lord Privy Seal and Leader of the House of Lords, admitted 'casual affairs' with prostitutes from a Mayfair escort agency but denied knowing Norma Levy.^[7]

A security inquiry on the prostitution scandal concluded that there had been "nothing in (Lambton's) conduct to suggest that the risk of indiscretions on these occasions was other than negligible". Lambton stated that he had never taken his red state boxes of government documents with him when he visited Norma Levy. The security inquiry was held due to fears that the prostitution scandal may have involved an actual or potential breach of national security (as had occurred in the Profumo scandal in the 1960s).

When Lambton was interviewed by MI5 officer Charles Elwell, Lambton first claimed that the pressure of his job as a minister was what drove him to procure the prostitutes. Later, Lambton stated that his sense of "the futility of the job" and lack of demanding tasks as a junior minister were reasons he went to prostitutes. Finally, Lambton claimed that his judgment was faulty when he went to the prostitutes due to his obsession with the battle over the use of an aristocratic title that had been used by his father; Lambton claimed that he sought to soothe this obsession by engaging in activities such as gardening and debauchery.^[8]