NDP Leader Thomas Mulcair has written an open letter to federal Heritage Minister Mélanie Joly urging her to keep the Liberal promise of restoring $150 million in funding to CBC/Radio-Canada.

Last week, in an interview with the Huffington Post, Joly refused to say specifically how much the government would raise the budget by for the CBC and its French-language arm Radio-Canada.

"One thing is certain: Radio-Canada is really a priority for us and we are working hard to substantially increase the funding," Joly told the Huffington Post.

When asked if the Liberals would offset the former Conservative government's $115 million cuts to the broadcaster, she repeated, "I am working very hard to increase Radio-Canada's budget."

In his letter to Joly, Mulcair writes, "It is now time to take action and fulfil your promise to increase funding by $150 million in your government's first budget. After years of deep cuts, it is unacceptable for the cultural sector to face this kind of uncertainty once again."

In a budget handed down in 2012, the then Conservative government of Stephen Harper cut $115 million from CBC funding over three years. Since then, the broadcaster has been hit by layoffs and program cancellations.

In 2014, the CBC eliminated more than 650 jobs, and then said it would cut an additional 1,000 to 1,500 jobs by 2020. At that time, it had 7,500 employees.

During last year's election part of the Liberals' platform was to "reverse Stephen Harper's cuts and invest $150 million in new annual funding for CBC/Radio-Canada, to be delivered in consultation with the broadcaster and the Canadian cultural community."