The Munitions of War Act 1915 was a British Act of Parliament passed on 2 July 1915 during the First World War. It was designed to maximize munitions output and brought private companies supplying the armed forces under the tight control of the newly created Ministry of Munitions, under David Lloyd George. The policy, according to J. A. R. Marriott, was that:
no private interest was to be permitted to obstruct the service, or imperil the safety, of the State. Trade Union regulations must be suspended; employers' profits must be limited, skilled men must fight, if not in the trenches, in the factories; man-power must be economize by the dilution of labour and the employment of women; Private factories must pass under the control of the State, and new national factories be set up. Results justified the new policy: the output was prodigious; the goods were at last delivered.The law imposed very strong regulations on wages, hours and employment conditions. It was a penal offence for a worker to leave his current job at such a "Controlled Establishment" without the consent of his employer, which in practice was "almost impossible" to obtain. The Clyde Workers' Committee was established to oppose the Act.
The Munitions Act was a response to the Shell Crisis of 1915 when inadequate supplies of artillery shells and other munitions caused a political crisis for prime minister H. H. Asquith and the formation on 17 May 1915 of a coalition government of all three major parties.
The Act forbade strikes and lockouts and replaced them with compulsory arbitration. It set up a system of controlling war industries. It established munitions tribunals that were special courts to enforce good working practices. It suspended, for the duration, restrictive practices by trade unions. It limited labour mobility between jobs. The courts ruled the definition of munitions to be broad enough to include textile workers and dock workers. The law was repealed in 1919, but similar legislation took effect during the Second World War.
In 1919, as promised in 1915, the main features of the law were abolished regarding manning arrangements, closed shop agreements, restriction of overtime and apprenticeship rules.