With the WA Government and opposition approving to widen trading hours across the city, Perth is set to abscond the "dark ages" behind.

Labor Leader, Eric Ripper proclaimed that he had reached in-principle conformity with Premier Colin Barnett to permit shops to remain open until 9pm on weeknights. The plan would also allow more shops to trade on Sundays.

The agreement came practically a year after a prior effort by Mr. Barnett to enlarge retail trading hours to 9pm was discarded by Mr. Ripper and the Labor caucus.

Mr. Barnett criticized the opposition's decision in August last year, saying they were stuck in the 'dark ages'.

"The Labor Party should be ashamed of itself for not being able to stand up for their constituents. Why are you so far back in the dark ages", he had questioned the Parliament.

Under the recently granted plan, all retail shops and supermarket chains will be permitted to open until 9pm on weeknights while shops selling 'durable consumer goods' such as white goods will be able to trade on Sunday, as well.

Mr. Ripper said the particulars of the plan were still being conferred but the rule to extend trading hours was clear. He said the key constituent of the negotiation was the rendezvous of a small business commissioner.