Egyptian prosecutors have demanded the maximum penalty for Australian journalist Peter Greste and his 19 co-accused who are on trial in Egypt.

The parents of an Australian journalist on trial in Egypt say they’re prepared for the worst after prosecutors demanded the maximum penalty for all defendants in the trial.

Prosecutors say they want penalties ranging from 15 to 20 years’ jail for all 20 defendants, including Peter Greste, in the trial of Al Jazeera journalists accused of aiding the blacklisted Muslim Brotherhood.

Mr Greste’s parents told reporters in Brisbane on Friday that although they know their son is innocent they are still prepared for the worst.

“The best case scenario would be that he would be let free and he was acquitted,” his mother Lois Greste said.

“We’ve had curve balls come at us all the time over the past six months and I think that we’ve got to be prepared for a possible committal, a sentence.”

Juris Greste added: “Obviously from our point of view there cannot and should not be any other outcome but complete acquittal.

“And yet … one of the many things that we have learned is to absolutely expect the unexpected at any time.”

Greste and two other detained reporters with Qatar-based Al Jazeera English are among the accused, in a trial that has triggered international outrage amid growing fears of media restrictions in Egypt.

“We request that the court, without compassion or mercy, apply the maximum penalty for the abominable crimes they have committed … mercy for such (people) will bring the entire society close to darkness,” prosecutor Mohamed Barakat told an Egyptian court on Thursday (local time).

The prosecution has charged the 16 Egyptian defendants with joining the Muslim Brotherhood, designated as a “terrorist group”.

The four foreign defendants in the case, including Greste, are charged with “spreading false news”, collaborating and assisting the Egyptian defendants in their crimes by providing media material, editing and publishing it on the internet and Al Jazeera.

Nine of the 20 defendants are in detention, while others are being tried in absentia.

The 16 Egyptians could get prison terms of 25 years, while the four foreigners could be jailed for 15 years, according to defence lawyer Ibrahim Abdel Wahab.

Greste and Mohamed Fadel Fahmy, the Cairo bureau chief of Al Jazeera English, were arrested in a hotel room in the capital on December 29 after the channel’s office was raided by police.