In 1968, Robson became President of the Women's Liberal Federation, standing down in 1970 when she was elected President of the Liberal Party. As president, she opposed radicalism and, in particular, the policies advocated by the National League of Young Liberals. She was created Baroness Robson of Kiddington, of Kiddington in the County of Oxfordshire on 14 May 1974, becoming the Liberals' spokesperson on agriculture and the environment in the House of Lords. In 1982, she succeeded her husband as Chair of the National Liberal Club, and also as Chair of the Anglo-Swedish Society. She joined the Liberal Democrats, successors of the Liberal Party, and in 1988, she chaired a panel investigating fraud in the European Union. She stood down as a magistrate in 1989, by which time she was the longest-serving magistrate in the country. In 1993, she became the party spokesperson on health.
