In 1699, Erle lost one of his regiments and returned to Ireland as second in command to Lord Galway. He was appointed an Irish Privy Councillor. He was returned again as MP for Portsmouth in the two elections of 1701. However at the second election of that year, Erle was also returned as MP for Wareham and chose to sit there. He brought in the mutiny bill on 5 February 1702, and told against an amendment to it on 16 February. Erle was given leave to go to Ireland on 4 March 1702, having been appointed Commander-in-Chief of the land forces in Ireland under the Earl of Rochester. He was made a Lord Justice of Ireland and then promoted to Lieutenant-General. Erle stood again at Warham and Portsmouth at the 1702 English general election and chose to sit for Wareham again.