He was member of the Irish Parliament for Hillsborough (1771–1776) and County Monaghan (1783–1800).

[2] He was the son of Robert Leslie and Frances (née Rogerson), daughter of Sir John Rogerson, Lord Chief Justice of Ireland, and Elizabeth Ludlow, niece of the regicide Edmund Ludlow.

In 1765, Leslie married Prudence Penelope, daughter of Arthur Hill-Trevor, 1st Viscount Dungannon and Anne Stafford.

His children from this marriage included Charles Powell Leslie and Rev.

In 1785, he married Mary Anne (née Tench) with whom he had one son and four daughters.