Promoted to lieutenant general in 1709, Boyle became Deputy Governor of Dover Castle later that year and was then given command of a secret but abortive expedition to attack New France in 1710. As the Earl of Scarborough was no longer in a position to nominate both members for Arundel, Boyle changed constituency to Hythe for which seat he was nominated by Lionel Sackville, 1st Duke of Dorset, in 1710. In Parliament, in accordance with Whig party policy, he voted for the impeachment of Henry Sacheverell, a clergyman who had criticised the party, in March 1710.