More than 1000 childcare workers will walk off the job on International Women's Day on Wednesday to draw attention to the large pay gap between male- and female-dominated professions.

Dozens of childcare centres will close mid-afternoon to support the national campaign, which is the largest walk-off by early childhood educators and follows a similar action held on Equal Pay Day last year.

Qualified early childhood educators earn as little as $20.61 an hour, about half the national average wage and significantly less than workers in male-dominated professions with comparable skills and qualifications.

Childcare union United Voice has a long-running wage case in the Fair Work Commission, arguing that the 97 per cent female workforce is under-paid for working in a "pink collar" sector.