Salisbury Convention

The Salisbury Convention (officially called the Salisbury Doctrine, the Salisbury-Addison Convention or the Salisbury/Addison Convention) is a constitutional convention in the United Kingdom under which the House of Lords should not oppose the second or third reading of any government legislation promised in its election manifesto.

The origins of the convention date back to the late 19th century, at which time the Conservatives held a majority in the House of Lords and, with the support of the third Marquess of Salisbury, developed the "Referendal Theory", which applied solely to Liberal legislation, under which the House of Lords could obstruct legislation until it had received majority approval at a general election. This was changed following the landslide Labour Party victory in the 1945 general election, which produced a Labour government seen as having a popular mandate for significant reform, while once again there was a Conservative majority in the House of Lords. The fifth Marquess of Salisbury (grandson of the third) announced that the Lords "would not seek to thwart the main lines of Labour's legislation provided it derived from the party's manifesto for the previous election". From this point, manifesto bills were only to be adjusted by the Lords; however, on non-manifesto bills, the Lords were able to act as they had before.

Prior practice

From the Liberal split over the Irish Home Rule Bill 1886 until the effects of the House of Lords Act 1999, the second chamber had a Conservative majority (or, in later years, quasi-majority given the overall tendency of the crossbenchers to side with Conservatives) so manifesto commitments of the Liberal Party and Labour Party could not be sure of passing. Since the Lords threw out the Liberal budget in 1909, there had been a convention that they do not interfere on financial matters. In the Parliament Act 1911 the Peers lost their right to vote down a financial measure and their veto over other measures was reduced to a two-year delaying power, later reduced to one year by the Parliament Act 1949.

A Conservative majority of Lords used their maximum power, of delaying via wrecking amendments, certain Bills tabled by the 1929–1931 minority Labour ministry. Most legislation worked its way through by threatening use of the Parliament Act 1911.