Chamber of Commerce and Industry WA chief economist Rick Newnham, one of the business leaders instrumental in WA's successful GST campaign, is leaving his high-profile role to join one of WA's biggest companies.

Mr Newnham is leaving the chamber to join one of its biggest member organisations, Wesfarmers in a business development role.

He has been at the chamber since January 2017 after postings with Shell across the globe.

Mr Newnham led a relentless campaign with Perth's business community against WA's low GST share from 2017 to 2018, arguing the previous formula penalised WA for developing its natural resources while rewarding those who locked them up.