What's behind the push to expand the childcare subsidy and pay it to parents instead?

Australia spends billions of dollars a year subsidising childcare centres. But what if that money flowed to parents, instead of providers?The debate is gaining attention as a Senate inquiry investigates the quality and safety of Australia's early childhood system.Supporters say it would give families more choice, while critics argue it's not what's best for children. So how might an expansion of the childcare subsidy work, and how much would it cost?