Prentice took an interest in politics, and contributed to Cowdroy's Gazette, a weekly. In May 1821 the Manchester Guardian was founded as an organ of radical opinion. Some, including Prentice, found John Edward Taylor as editor insufficiently advanced; Prentice purchased Cowdroy's Gazette to start an alternative paper. In June 1824, the first number of the renamed Manchester Gazette appeared under his editorship.
