Nassau William Senior in the context of "Hermann Heinrich Gossen"

The Poor Law Amendment Act 1834 (4 & 5 Will. 4. c. 76) (PLAA) known widely as the New Poor Law, was an act of the Parliament of the United Kingdom passed by the Whig government of Earl Grey denying the right of the poor to subsistence. It completely replaced earlier legislation based on the Poor Relief Act 1601 (43 Eliz. 1. c. 2) and attempted to fundamentally change the poverty relief system in England and Wales (similar changes were made to the poor law for Scotland in 1845). It resulted from the 1832 Royal Commission into the Operation of the Poor Laws, which included Edwin Chadwick, John Bird Sumner and Nassau William Senior. Chadwick was dissatisfied with the law that resulted from his report. The Act was passed two years after the Representation of the People Act 1832 which extended the franchise to middle-class men. Some historians have argued that this was a major factor in the PLAA being passed.

The act has been described as "the classic example of the fundamental Whig-Benthamite reforming legislation of the period". Its theoretical basis was Thomas Malthus's principle that population increased faster than resources unless checked, the "iron law of wages" and Jeremy Bentham's doctrine that people did what was pleasant and would tend to claim relief rather than working.