[2] Acheson sat in the Irish House of Commons for County Armagh from 1798 until the Act of Union in 1801, when Ireland became part of the United Kingdom.

Subsequently, he was a Member of the British House of Commons representing Armagh to 1807, when he succeeded to his father's Irish titles as Earl of Gosford.

He was created Baron Worlingham in the Peerage of the United Kingdom in 1835 and thus became a member of the UK House of Lords in his own right.

Gosford attempted to distance himself from his predecessor, Lord Aylmer, who had exacerbated the hostility of French-Canadians to the British administration.

The next month, he issued a reward for the capture of Papineau, and declared martial law in Lower Canada.