the peirse family had controlled one seat at northallerton since the 17th century. while peirse was under 21 the lascelles family were allowed both seats. when he came of age he reclaimed his seat and at the 1774 general election was returned as member of parliament for northallerton. he counted himself a whig and joined brooks's in 1778. in 1779 the public ledger described him as ‘a gentleman of very good character, and attached to opposition from principle and conviction’. he was a member of the st. alban's tavern group which in january 1784 tried to bring together fox and pitt. although his attendance remained somewhat unpredictable he voted in many of the major issues. his final election was in 1820.