The sixth season of Offspring has started production in Melbourne, with the show picking up the story of the Proudman family 18 months after the baby-congested finale of season five.

The show's protagonist Nina, played by Asher Keddie, has a toddler on her hands, with baby Zoe now two-and-a-half years old.

"With the Proudman family rocked by a heart-breaking event, Nina's story and her unpredictable, messy and often hilarious life continues," according to a Network Ten press release.

Production company Endemol Shine said the new series will return to the show's familiar themes: "Following the death of Patrick, Nina is determined to jump back into life. While raising her daughter, along with the help of unruly elder sister Billie (played by Kat Stewart), Nina rediscovers the joy and romance of life and continues her tendency to over-think and fly off into fantasy."

The cast also includes Lachy Hulme, Patrick Brammall, Deborah Mailman, Eddie Perfect and Lawrence Leung.

New cast members include TJ Power as lawyer Will Bowen, while Dan Wyllie guest stars as Dr Angus Freeman, St Francis' Director of Clinical Education.

Perfect, who plays the role of Mick Holland, told Fairfax Media earlier this month he had not read the scripts for the new series.

But he said: "Asher's so completely across the show and across that character and she would just not want to do it at all, no one would want to do it if it was going to be crap. I was like 'If they're bringing it back, it must be good.'"

Offspring creator Debra Oswald announced last September she would not take part in season six.

"I'm happy with where we took the story by the end of Offspring 5, so I've chosen not to be part of S6," Oswald wrote on social media.

The latest series, due to air later this year, will be more expensive for Network Ten to acquire from producer Endemol Shine.

The show no longer qualifies for the producer offset, a federal government program that allows a tax rebate of 20 per cent of production costs, because more than 65 episodes had been produced.

"Obviously the show is now so popular that paying a higher price for it is obviously a consideration," producer John Edwards said in 2014.