Opposition Leader Matthew Guy, who as planning minister approved some of the city's biggest and most controversial developments, says Melbourne is growing too quickly.

"Melbourne can't afford to be an unlivable city of seven-plus-million people," said Mr Guy, who was planning minister from 2010 to 2014. "That's not the kind of city we should be leaving our children but it's the kind of city we are headed toward."

Opposition leader Matthew Guy. Credit:The Age

Mr Guy's comments – which come amid a sharp rise in concerns over Melbourne's population boom – were made on Monday as he announced he would change the city's zoning laws if he wins November's state election.

The changes would bring back zoning rules Mr Guy introduced when he was in office, making it harder to build medium-density housing on established streets by imposing a two-dwelling limit.