A public inquiry into how a British family doctor murdered over 200 mostly elderly patients will reveal on Thursday whether he claimed another 137 victims.

The final report of the probe into Dr Harold Shipman will report on suspicions that he could have murdered more patients while working as a junior hospital doctor in the 1970s, prior to his notorious killing spree as a family practitioner.

British newspapers said last week four babies were among another 137 deaths investigated by the inquiry into Shipman, Britain’s most prolific serial killer.

Judge Dame Janet Smith, heading the inquiry, originally concluded that there had been no suspicious deaths while Shipman worked at Pontefract General Infirmary in northern England.

But an unnamed health official last year voiced suspicions about Shipman, nicknamed “Dr Death” for the cold and systematic way he murdered his victims with heroin injections over a period of 23 years.

Lawyers from the Manchester-based inquiry have spent months tracking down relatives of patients who had their death certificates signed by Shipman while he was at Pontefract.

“The inquiry looked at 137 deaths because that’s the number of deaths he certified during his time at Pontefract,” a spokesman for the Shipman Inquiry said.

Shipman was convicted in 2000 of murdering 15 of his patients and sentenced to life in prison. An inquiry later ruled that he had murdered at least 215 of his patients.

Shipman hanged himself last January in his cell at Wakefield prison where he was serving 15 life sentences.

The inquiry’s first report found that Shipman had quietly murdered his victims, ending the life of patient after patient in a betrayal of trust “unparalleled in history”.

His motives remain a mystery and he consistently refused to confess to any of them.