On his father's death in 1811, Fielden and his brothers inherited the family cotton-spinning business at Todmorden, which became one of the greatest manufacturing concerns in Great Britain. Unlike most mill owners, Fielden soon became a supporter of legislation to protect factory labour. Declaring himself a radical, he won a seat in the House of Commons in the first general election after the Reform Bill passed in 1832. Fielden voted for every radical proposal. He vigorously opposed the New Poor Law of 1834 and was the main Lancashire spokesman for limiting the working day. Triumphantly returned to Parliament in 1835, 1837, and 1841, he devoted his main energies to the local and national struggle to resist the introduction of the poor law and to the fight for a ten-hour working day bill. He sponsored the successful Ten Hours Act of 1847 but was defeated at the general election of that year and retired from politics.