Mr Johnson was responding to a query from Leigh’s Tory MP James Grundy on the environmental plan, put forward during Wednesday afternoon’s Prime Minister’s Questions.
The Prime Minister said in response to Mr Grundy that while trying to clean up air in cities, it was important not to penalise businesses, and he branded the GM plan ‘unworkable’ - while advising Environment Secretary George Eustice would say more in the coming days.
Mr Johnson added: “We must find an alterative that doesn’t punish local residents.”
It comes as local taxi drivers announced plans to protest in Manchester city centre tomorrow ahead of a meeting about the Clean Air Zone.
The air zone scheme is designed to tackle air pollution levels across Greater Manchester. It does not apply to private cars but will see other non-compliant vehicles charged for using the roads.
Following a backlash online, including from some business owners, Mayor Andy Burnham met with the Government to discuss the roll-out last week and said to expect an update within 10 days. Concerns have been raised over funding and supply issues around compliant vehicles.