The former children’s entertainer and artist Rolf Harris is to be retried on three sexual offence charges on which a jury were last week unable to reach a verdict, and will face one new count.

The jury found the 86-year-old Australian not guilty of three assaults after a trial at Southwark crown court in London but they were discharged from deliberating further on four undecided counts.

On Wednesday morning Harris appeared again at Southwark via video link to hear Julia Walker, prosecuting, tell Judge Alistair McCreath a retrial was sought on three of the undecided charges plus an extra count related to one of the complainants.

The claims relate to alleged incidents involving a 14-year-old girl at the Lyceum theatre in London’s West End in 1971, a 16-year-old during the filming of ITV’s Star Games in 1978, and a 13-year-old in the green room of the BBC’s Saturday Superstore in 1983. One count of indecent assault, relating to a 19-year-old backing singer at a rehearsal studio in London, has been dropped by the Crown Prosecution Service.

McCreath, who will retire before the trial, said: “We will need to discover who the trial judge is to be – I shall be history by then.”

He added: “Mr Harris, you have been listening to this I’m sure, the retrial will take place on 15 May, I have I think formally remanded you in custody in the meantime.”

A spokesman for the CPS said it had decided to seek a retrial after careful consideration. “This decision was taken after consideration of all the matters set out in our legal guidance on seeking retrials when a jury has failed to agree on a verdict,” he said.

“The Crown Prosecution Service reminds all concerned that criminal proceedings against Rolf Harris remain active and that he has a right to a fair trial. It is extremely important that there should be no reporting, commentary or sharing of information online which could in any way prejudice these proceedings.”

