The British Parliament Act of 1911 cut the powers of the House of Lords to interfere with and retard House of Commons legislation, asserting the supremacy of the Commons.
The act stopped the Lords from vetoing any public legislation, budgets or "money bills" (dealing with taxation) that had been approved in the Commons and restricted their ability to delay other legislation to one month for money bills and two years for other public bills. The delay was that the rejected bill would become law without the consent of the Lords, if passed by the Commons in three successive sessions, providing two years elapsed between Second Reading and final passing in the Commons. The only bill they could veto was one to prolong the lifetime of a parliament. The bill also changed the maximum duration of any parliament from seven years to five and provided payment for MPs.
This bill was brought on by the clash between the Liberal government and the Lords, culminating in the so-called "People's Budget" of the chancellor David Lloyd George in 1909, which proposed the introduction of a land tax based on the ideas of the American tax reformer Henry George. This would have had a major effect on large landowners and the Conservative opposition which consisted mostly of large landowners had a large majority in the Lords. Furthermore they believed that money should be raised through the introduction of tariffs on imports, thus helping British industry. They voted down the new budget. They did so, and the Liberals built on the unpopularity of the Lords to make the issue of the 1910 General Election reducing the power of the Lords. The Liberals won the election and used this mandate to introduce the Parliament Act. However the Land tax proposal was quietly dropped.
When the House of Lords attempted to stop the passage of the bill, the new Prime Minister, Herbert Henry Asquith, went to George V. The king agreed with Asquith that, if necessary, he would create 250 new Liberal peers to neutralise the Conservative majority in the Lords. The Conservative Lords then backed down.
The 1911 Act was amended in 1949 to reduce the power of the Lords further by cutting the time they could delay bills from two years to one. The Lords attempted to block this change and the 1911 Act had to be used to force it through. Some doubts have been raised as to whether this was valid, as if the restriction on the Parliament Act being used to prolong the life of Parliament were to be effective then it would have to be entrenched (as otherwise the Commons could first use the Parliament Act to abolish that part of the Parliament Act, then use the amended Parliament Act to abolish elections). However the wording of the Act implies no such entrenchment.
The Acts have been used only a handful of times. In 1914 the Welsh part of the Church of England was disestablished as the Church in Wales, and an Act was passed to establish a Home Rule government in Ireland (the implementation of this was blocked due to the First World War). In 1991 the War Crimes Act was passed with the Act, extending jurisdiction of UK courts to cover acts committed on behalf of Nazi Germany during the Second World War. In 1999 an Act was passed to change the system of elections to the European Parliament to a form of proportional representation. The most recent use of it was to equalise the age of consent for homosexual relationships with that of heterosexual ones at 16.