By Andrew Brown in Canberra

Discounted pay rates for young adults working in sectors such as fast food, pharmacy and retail have been scrapped in a workplace watchdog decision.

The Fair Work Commission on Tuesday said employees aged from 18 to 20 should receive the full award wage.

Currently, wages for 18-year-olds in those sectors are 70 per cent of the full award wage, rising to 80 per cent for those aged 19, and 90 per cent when they reach 20.

Junior wages will still remain in place for minors.

The higher wages for junior workers will start to be phased in over a four-year period from December.

The commission said there would be no changes to wage rates for workers aged 18-20 who had less than six months of experience at their current workplace.

The decision took into account factors such as labour market disadvantages for young people, the watchdog added.