Robert Doyle, the lord mayor of Melbourne, is seriously ill, which will delay the investigation and report into sexual assault allegations against him.

Doyle, who is the city’s longest-serving lord mayor and a former Victorian Liberal leader, went on extended leave in December after his council colleague, Tessa Sullivan, resigned and alleged that Doyle had sexually harassed and indecently assaulted her.

Another councillor, Cathy Oke, told city investigators that Doyle had once tried to kiss her and on another occasion had clutched her thigh under a table. A second investigation into Doyle was announced by the state’s health minister, Jill Hennessy, in January after reports by Fairfax Media that a third woman had come forward alleging Doyle sexually harassed her at the Melbourne Health medical awards ceremony in 2016. Doyle is chair of the board of Melbourne Health.

On Friday the city of Melbourne issued a statement saying its investigation into Doyle would report in two stages owing to his poor health. The council’s chief executive officer, Ben Rimmer, said the council wished Doyle a “full and speedy recovery”.

“We are very conscious of the need to support all councillors and employees during this difficult time,” he said.

“We recognise that the investigative process has been extremely stressful for all parties and their families, despite the best efforts of the city of Melbourne and the independent investigation. Unfortunately some media reporting has exacerbated this impact.

“I urge media outlets to consider that the public interest is best served by allowing the current investigative and reporting processes to conclude unhindered without the publication of inflammatory, damaging or speculative information or commentary.”

The council’s future Melbourne committee will be provided with an update on the status of the investigation at a meeting on Tuesday. This update report states that deficiencies had been found in the council’s councillor code of conduct.

“Management recommends the code be reviewed by council, particularly in relation to reporting and management of sexual harassment allegations and occupational health and safety matters involving councillors,” it states.