An Australian man who had sought the maximum jail term for murdering his mother has called his sentence of at least 17 years "manifestly inadequate."

Adam Patrick Owens, 36, had pleaded guilty to the stabbing murder of his mother, 69-year-old environmentalist Doris Owens, in her home at Swanhaven, on the New South Wales south coast, in September 2006.

Earlier this month, he told the NSW Supreme Court his only regret was that he hadn't murdered her 20 years earlier, and that he would do it again if he had his time over.

During that hearing, his lawyer told the court an "extremely substantial sentence is appropriate ... it seems to me you must apply the maximum."

In sentencing Owens today, Justice Lucy McCallum said she could not believe such a request had come from someone of sound mind.

When she entenced Owens to a minimum of 17 years in prison he called out, "Manifestly inadequate."

His mother was found in her bed with seven stab wounds, fractured ribs and defensive wounds to her hands.

Owens initially denied involvement in the murder until he confessed the killing to his brother Caleb Owens, in March 2007.

Click here to read more on this story from News.com.au.