Tessa Sullivan, who was elected on the same ticket as Cr Doyle, resigned from the council on Friday and lodged a complaint with the council's chief executive, Ben Rimmer.

Ms Sullivan alleges Cr Doyle sexually harassed and indecently assaulted her, including grasping her breast and making sexually explicit comments to her.

In a statement released on Twitter, Cr Doyle said he was shocked by the allegations, had not officially been informed of the specifics and would take a month's leave.

He said his decision to take leave "must not be interpreted as any concession or admission".

"I welcome the investigation and will co-operate fully to clear my name," he said.

"I have not been officially informed of the specifics but find the allegations detailed to me by media outlets thoroughly abhorrent, not only as lord mayor but as a father of young women, a husband, a brother and as the head of an office made up entirely of women."

"What is important now is that proper process be allowed to take place and that the rights of all involved are respectfully handled," Cr Doyle said. "This is an incredibly distressing time for me and my family."

The Age contacted Cr Doyle at 8:15am on Sunday, but did not receive a response until he tweeted his public statement at 1pm.

Lord mayor Robert Doyle said he was shocked by the allegations. Photo: AAP

The Age has also been told a second female colleague, who has not made a formal complaint, says that during a meeting in 2014, Cr Doyle clutched her upper thigh under a table.

This alleged incident was said to have been witnessed by another person at the meeting. On Sunday, this person confirmed to The Age that they had seen the lord mayor grasp this woman's leg. They had later asked the woman why she did not "call out" Cr Doyle for his alleged behaviour.

Ms Sullivan's complaint on Friday included a statement from the second woman, and a supporting statement from Ms Sullivan's friend Alicia Chisholm, a lawyer, who was present when Ms Sullivan disclosed the allegations in front of a fellow councillor at a social event.

In a statement on Sunday, council chief executive Ben Rimmer said he had commissioned an independent external investigation of these matters, led by Dr Ian Freckelton, QC, in accordance with natural justice principles.

"These allegations are very serious, and if proven, would be inconsistent with the values of the city and the organisation. Therefore it is very important that these matters are thoroughly investigated."

In a statement to The Age on Sunday, Ms Sullivan said: "Sexual harassment and indecent assault of women is unacceptable. I encourage women in politics to make a stand against such acts."

"I felt isolated for so long, I hope other women will feel strong enough to come forward, too. There needs to be a better system in place to protect women from such violations of safety, and a greater collective effort to ensure that this culture is eradicated."

Ms Sullivan's friend Jacqui Siebel, who works at a community legal centre, has confirmed to The Age she was present as a support person to Ms Sullivan on Friday when Ms Sullivan lodged her complaint against Cr Doyle.

Ms Siebel confirmed that Ms Sullivan lodged a complaint against Cr Doyle, alleging sexual harassment and indecent assault.

"Tessa was understandably upset," Ms Siebel said. "Because of the conduct, she was left to feel powerless. However, I consider her to be incredibly brave."

Tessa Sullivan, who resigned as a councillor on Friday. Photo: Melbourne City Council

Ms Sullivan joined the "Team Doyle" ticket for the 2016 elections.

Cr Doyle would allegedly compliment Ms Sullivan, comment on her clothing, hug and kiss her, and display overt affection in a way that she felt was not appropriate in a workplace.

Councillors meet for drinks together at Town Hall after council meetings on Tuesday nights, and on occasion Ms Sullivan would get a lift home from Cr Doyle and his driver. Cr Doyle would be dropped off at his home first, and then Ms Sullivan.

On a Tuesday night in May this year, Cr Doyle exited the car at his address and, it is alleged, opened the door to the back seat where Ms Sullivan was sitting.

He allegedly put an arm around her neck and then grabbed her breast with his other hand. She slapped away his hand, it is alleged.

In October this year, Ms Sullivan accompanied Cr Doyle to the lift at Town Hall after a council meeting, and said she would go down [in the lift] with him.

He allegedly replied, "Will you just?" and then allegedly said, "I love cunnilingus."

The councillors noticed that Ms Sullivan was tearful the next day, and asked her what was wrong. She did not divulge the alleged sexual harassment at that time.

She later confided Cr Doyle's alleged behaviour to her friend Ms Chisholm (who gave a supporting statement to council on Friday), and a number of her fellow councillors. She asked them not to reveal the allegations.

One councillor told Ms Sullivan that Cr Doyle had allegedly commented on Ms Sullivan's breasts, saying they had become smaller.

The Age has been told Ms Sullivan lost a considerable amount of weight in the past six months and has appeared anxious and unhappy, in contrast to her usual positive outlook.

Ms Sullivan is a lawyer, working in the areas of commercial and family law and speaks four languages. She is married and has three children.

Cr Doyle, 64, is married and has four children. He was elected lord mayor in 2008 and is a former state opposition leader.

Council chief executive Mr Rimmer, is a "Male Champion of Change", part of a national program that encourages male leaders of major organisations to take a stand against gender harassment and violence.

All council staff recently received an email from Mr Rimmer stating that he wanted Town Hall to feel like a place where all employees felt safe and supported, and all employees would have to take compulsory training on gender equality and family violence.

Now that Ms Sullivan has resigned, Team Doyle candidate Beverley Pinder-Mortimer is likely to be elected in her place, retaining the Team Doyle majority on the council.

Local Government Minister Marlene Kairouz's spokeswoman described the allegations as "extremely serious". She said the government fully supported the independent investigation into the matter.

Councillor Arron Wood will be acting lord mayor while Cr Doyle takes leave.

In a statement released Sunday night, Cr Wood said: "Like all councillors, I am very concerned by the allegations made public today and welcome the independent investigation that has been established by the chief executive officer. The investigation will be particularly important in providing natural justice to all parties."

In a tweet, the Royal Melbourne Hospital said Robert Doyle had advised the Department of Health and Human Services and the Melbourne Health Board that he would take a month's leave as the chair of Melbourne Health. Board member Jane Bell will serve as acting chair.

clucas@theage.com.au

mperkins@theage.com.au