David McLaren was born at Glasgow, Scotland, probably sometime between 1867 and 1872, the son of Jane Ayton and her husband, Robert McLaren, a baker. As a child David was delicate and nearly lost his eyesight, a faculty that remained impaired for the rest of his life.
The McLaren family emigrated to Dunedin, New Zealand, in the early 1880s, where David served an apprenticeship as a bootmaker. Influenced by his experiences during the depression, he became actively involved with the union movement and in 1893–94 was president of the Dunedin Operative Tailors' Society. During the mid 1890s he moved to Wellington and worked at various labouring jobs, spending some time on the swag. He considered this an important part of his education, instilling the need for self-reliance.
From the late 1890s labour politics became an important part of his life. Between 1896 and 1903 he belonged to a number of socialist groups, holding office in at least two. He cautioned, however, that he was 'no wild dreamer' but a 'Liberal and a Democrat'. He also renewed his involvement with trade unions and in 1897 was vice president of the local branch of the New Zealand Workers' Union. In 1899 he helped re-establish the Wellington Wharf Labourers' Union and became its first full-time secretary, a position he held for 10 years. In 1901 he became secretary of the Wellington Building Trades Labourers' Union, and in 1907 secretary of the Wellington Iron and Brass Moulders' Union.
McLaren had shown interest in standing at a parliamentary by-election in 1898, but failed to secure the Wellington Trades and Labour Council nomination. He had more success at entering local-body politics, winning a seat on the Wellington City Council in 1901 as an independent. At the 1905 general election McLaren unsuccessfully contested the Wellington East seat, but in 1908 stood on behalf of the Political Labour League of New Zealand, of which he was a national executive member, and won on the second ballot.
As the first independent Labour member of Parliament, McLaren attended the Liberal caucus but took an independent stand. He was a critic of imperialism, opposing the gift of a dreadnought to Britain and the introduction of compulsory military training. He frequently spoke on issues of concern to workers including unemployment, immigration and the land question, on which he supported leasehold rather than freehold. He accepted that the Industrial Conciliation and Arbitration Act 1894 was the best way of organising industrial relations, but criticised the way in which it worked in the interests of employers. McLaren's parliamentary career was short. In 1911 he increased his personal vote but was defeated by 65 votes on the second ballot.
He had, however, retained his seat on the Wellington City Council, and from 1910 to 1915 was a member of the Wellington Hospital and Charitable Aid Board. He stood for both bodies under a range of political denominations, including the New Zealand Socialist Party, the Political Labour League, the first New Zealand Labour Party and the United Labour Party. In 1912 he became the first Labour mayor of Wellington, but was defeated the following year.
On 11 March 1902, in Wellington, McLaren had married Alberta Dungey Lindegaard. Alberta shared his interest in politics and served on the Wellington Hospital and Charitable Aid Board from 1913 to 1919.
One of McLaren's most significant contributions to the labour movement was his involvement in the formation of national organisations. He played a crucial part in creating a viable labour party, becoming president of the first New Zealand Labour Party in 1911 and a member of the dominion executive of the United Labour Party in 1912. In the industrial field he was the key figure in establishing the New Zealand Waterside Workers' Federation in 1906 and its first secretary. In 1907 he became secretary of the New Zealand Iron and Brass Moulders' Association. He also worked to establish unity between the various national trade unions. In 1909 he was national organiser of the Trades and Labour Councils of New Zealand.
McLaren was an early advocate of unity between the Trades and Labour Councils and the more militant New Zealand Federation of Labour. While not a supporter of the militants, he believed, during 1910, that in the interests of unity the councils should be prepared to compromise with the more radical organisation. Yet he was increasingly out of step with the dominant mood of the labour movement. From 1910 he was frequently attacked, and in 1911 defeated by socialists in the watersiders' union, amid allegations that he had sold out striking workers at Patea. This attack effectively ended his involvement in the union movement.
McLaren became increasingly critical of militant strategy and believed the Waihi miners' strike of 1912 and the general strike of 1913 were dangerous and counter-productive. He thought workers would prefer to support a properly administered arbitration system than to take strike action. He blamed his defeat in the mayoral election on the actions of the militants. Ironically, by 1913, when there was wider support for unity within the labour movement, he felt that compromise with the militants was impossible and undesirable. He refused to accept the agreement thrashed out at the Unity Congress in July 1913 and tried to disrupt the congress, walking out with the rump of the United Labour Party, which remained aloof from the newly established Social Democratic Party. He became the ULP's full-time organiser and continued to attack the mainstream movement.
In 1914 McLaren sought re-election to Parliament on the ticket of the Wellington Labour Representation Committee, losing by 48 votes. The campaign was practically his last connection with the labour movement. He increasingly put his energies into the war effort, serving on the War Relief Association of Wellington and the Wellington Military Service Board. After the war he was a member of the commission investigating the 1918 influenza epidemic.
Having moved from the left to the right of the political spectrum, McLaren spent much of the rest of his life attacking the movement he had helped build. He broke away from his former associates and colleagues. In 1927 James Thorn, editor of the New Zealand Worker, stated that he and McLaren had once been close friends but 'now he glowers at me like a chill wind from the Arctic Ocean'. McLaren believed that the labour movement was dominated by dangerous socialists and revolutionaries. He was also critical of a class analysis of society, preferring to promote common interests rather than conflict and division. After the war he became the full-time national organiser for the vehemently anti-labour New Zealand Welfare League and a leader of its local-body equivalent, the Wellington Civic League.
McLaren spoke with force but had a mournful and booming delivery. While his outward appearance was considered solemn, he possessed a good sense of humour and loved poetry. He was active in the Wellington Burns Club, occasionally lecturing on the bard. He died on 3 November 1939 at Wellington, survived by his wife and a daughter.