Paying 20-year-old workers at the same rate as 21-year-olds will “kill jobs” and rend the already struggling retail sector, an industry lobby says.

The comments are in response to a Fair Work Commission (FWC) decision, which found that as the roles of 20-year-olds are the same as 21-year-olds, they should earn the same rate of pay.

The change will be phased in over two years, amounting to an extra $1.80 an hour for part-time workers and $2.25 an hour for casual workers after at least six months.

But the Australian Retailers Association (ARA) says it practically spells the end for retailers, and is now pushing the federal government to fast track changing it back.

“This junior wage increase will severely hit retailers financially, as well as change the face of employment for 20 year olds,” ARA Executive Director Russell Zimmerman says.

Mr Zimmerman has accused the former government of designing the outcome of the Fair Work Commission’s review.

“The former government should be ashamed,” he said.

“They provided the FWC with deliberately misleading information... and supported a flimsy case when they took the polar opposite approach to the ARA’s application to allow some relief on Sunday penalty rates.”

“What retailer is going to employ a young Australian without any experience in the industry, when they can employ someone a few years older with more experience for exactly the same wage?” he asked.

Fair Work Commission senior deputy president Alan Boulton said in the ruling that the impact to employers was ultimately assessed as “moderate”.

“We are not persuaded that the provision of adult rates to 20-year-old retail employees will have a significant negative impact on business costs, nor on the viability of retail businesses,” he said.

“We are not persuaded it will have a discernible impact on employment growth.”

The case was brought to the FWC by the Shop, Distributive and Allied Employees Association (SDA), a workers’ union standing on behalf of younger staff.

SDA says the move was a step towards its goal of paying all workers over 18-years-old at the full rate of pay.

“The Fair Work Commission has revealed it agrees with what we’ve been saying for a long time – that paying younger workers less than the full adult rate is an outdated and discriminatory act that needs to be rectified,” SDA National Secretary Joe de Bruyn said.

“For too long employers have been getting away with paying workers less than what they deserve. It’s fantastic that the Fair Work Commission has recognised that. We can now look towards putting this into practice in the industry.”

Employment Minister Eric Abetz has so far declined to comment.