Former Catholic priest David Edwin Rapson has had his child sex abuse convictions quashed and been granted bail ahead of fresh trials.

Rapson, 61, was jailed for 13 years in 2013 for rape and sexual assault offences involving eight boys at two Victorian Catholic colleges between the 1970s and 1990.

But he was released on bail on Wednesday after the Victorian Court of Appeal quashed his convictions when the prosecution conceded the charges should not have been dealt with in the one trial.

He will now face fresh trials in the Victorian County Court.

The Office of Public Prosecutions (OPP) concedes the charges against Rapson should have been heard in separate trials, rather than just one.

Prosecutor Peter Kidd SC told the appeal court Rapson should now face three separate trials on the charges.

But Rapson's barrister Paul Holdenson QC argued that there should be separate trials for each of the eight victims.

Mr Holdenson told the court the alleged "modus operandi" for each of the victims was different.

While one set of charges allegedly involved "deception and trickery", Mr Holdenson said other allegations featured the "express use of authority in combination with the use of force".

Rapson allegedly drugged hot chocolate and soft drinks which he gave to the children before sexually violating them, the court heard.

Mr Holdenson said other allegations involved Rapson inducing children with alcohol and cigarettes and others the use of violence.

"There's not enough distinctiveness in the nature of the alleged sexual misconduct," Mr Holdenson said.

Court of Appeal President Justice Chris Maxwell and Justices Geoffrey Nettle and David Beach ordered Rapson's retrial and granted him bail.

The judges said it was for the trial judge to determine how many trials Rapson faces.

Victorian County Court Judge Liz Gaynor in October jailed Rapson for 13 years after he was found guilty of five charges of rape and eight counts of indecent assault against eight boys.

He was sentenced to a non-parole period of 10 years.

The OPP was obliged to change its stance on the number of trials Rapson should face after a Court of Appeal finding clarified the law earlier this month.

Rapson was not present in court.