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 and which had a large majority in the Lords, made it clear that they would halt 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.