The alliance of 15 organizations launched a campaign at city hall on Monday to inform the public about the ban's shortcomings.
Spokesman Kevin Gaudet says eliminating plastic bags will cause job losses in the plastic manufacturing industry, including family-owned small businesses.
The coalition says the ban won't reduce pollution, as some supporters have argued.
The group says consumers will start using more paper bags, which don't recycle well and consume three times the energy to produce.
The ban, which council narrowly voted in favour of last June, is set to go into effect on Jan. 1.
Mayor Rob Ford is a vehement critic of the ban, and city solicitor Anna Kinastowski has warned it could spark legal action.
The Ontario Convenience Stores Association has already threatened to take the city to court on the grounds that the ban violates the charter of rights and freedoms.
The coalition urges Torontonians to visit its website, www.reversethebagban.ca, to read up on the potential impact of the ban and air their opinions directly to council.