Child care and labour organizations want the federal government to scrap a proposal to extend parental leave to 18 months.
They say it would be problematic for employers, and would do little to actually help Canadian parents.
The government has received similar criticism from small business owners.
The Liberals proposed extending parental leave from the current 12 months to allow parents to spread out their benefits over a longer period.
Advocates instead want more benefits for new parents, dedicated time-off for fathers and a lower benchmark for new mothers to qualify for maternity leave.