Ontario's Liberal Party trumpeted the need to protect full-day kindergarten on Wednesday, as registration opened for the program's second year.

More than 50,000 children between the ages of four and five are currently enrolled in full-day kindergarten, five months after the initiative went into effect.

By September, 800 schools will offer full-day learning, easing the half-day childcare burden for parents. By 2015, every elementary school in Ontario is expected to have the option.

The full-day kindergarten program is shaping up to be a key campaign issue in October's provincial election.

Education Minister Leona Dombrowsky warned the program could suffer setbacks if the Conservatives form the government in October's provincial election.

"Our very distinct worry is that we are looking in phase 3 to have 50 per cent of the junior and senior kindergarten students in Ontario accommodated. I would say that is very much at risk," she said while visiting the Holy Name School in Toronto on Wednesday.

The Conservatives say that if they win the election, they will freeze the rollout and look for other, less expensive options.

It is expected to cost between $1 and $2 billion a year to operate the program.

Father Paul St. Pierre says full-day classes have cut down on the stress parents suffer.

"The full-day kindy actually cuts down on the worry by not having to think of where the child is going next. There is no transition from one place to another," St. Pierre told CTV Toronto. "That alone is excellent."

With a report from CTV Toronto's Paul Bliss