Mississauga's city council made its intentions clear earlier this year and two months later, Brampton has taken its stand.
Brampton's council voted to maintain Peel Region Tuesday night, in contrast with Mississauga's, which in March supported its mayor Bonnie Crombie's motion to leave.
Crombie has said Mississauga has given millions of dollars to Peel Region's other cities such as Brampton and Caledon, when it should be focused on its citizens.
But Mayor Patrick Brown said it's in all citizens best interest to remain.
"It saves families funds by sharing the cost of policing or water treatment," he told CP24. "Brampton has done their homework to make sure that it's based on facts and evidence."
Crombie says Mississauga has contributed $85 million to other cities and should stand alone like other municipalities like London and Guelph.
But Brown says according to recent audits, Mississauga is using old outdated information.
"The mayor of Mississauga is using numbers from 2004 and things have changed, Brampton's population has skyrocketed," he said. "If it's not broken, don't fix it."
The province has the final say and Brown said he expects the Ford Government will make its decision by August before the Association of Municipalities of Ontario's Annual Conference.