The right hon. Gentleman has argued, that the adoption of the plan proposed by the Government would confer advantage on the consumer, would increase the revenue, and would give increased scope to the industry of the manufacturer. We, Sir, argue, that with an amount of benefit to the revenue altogether inconsiderable, with a slight, nay an imperceptible relief to the consumer, and with detriment to the sure interests of the British manufacturer, you are asked to abandon what is nothing less than a great principle of humanity, that has received the most solemn sanction of the Legislature, the principle of hostility to the slave-trade and to slavery.
Speech in the House of Commons (10 May 1841). Gladstone was opposed to the equalisation of the duty on foreign and colonial sugar because he believed that it would promote the slave trade