Downing Street has contacted a TV producer who claims she was groped during a meeting inside Number 10, to ask whether she would like to make a formal complaint.
Daisy Goodwin, the creator of hit ITV series Victoria, said an official touched her breast after a discussion of a proposed TV programme during David Cameron's time in office.
The former prime minister has said he was "alarmed and shocked" to hear her allegations, and has contacted the Cabinet Office to voice his concern.
Downing Street said the Cabinet Office would look into any formal complaint that was made.
Theresa May's official spokesman declined to say whether any complaint had been received and said it would be "inappropriate" for him to disclose whether Ms Goodwin was being approached.
But a Whitehall source indicated that contact had been made with the TV producer to ensure she was aware that if she chose to make a complaint, it would be looked into.
Ms Goodwin told the Radio Times that she did not report the alleged incident at the time as she did not feel "traumatised", but was no longer sure whether she was right to keep quiet.
She said she was astonished when the official put his hand on her breast after the one-on-one meeting, and dealt with the situation by "humiliating" him verbally, looking at his hand and saying: "Are you actually touching my breast?"
"He dropped his hand and laughed nervously," she said. "I wasn't traumatised, I was cross, but by the next day it had become an anecdote, The Day I Was Groped In Number 10.
"Now, in the light of all the really shocking stories that have come out about abusive behaviour by men in power, from Hollywood to Westminster, I wonder if my Keep Calm And Carry On philosophy, inherited from my parents, was correct? The answer is, I am not sure.
"I think humiliating the official was probably the appropriate punishment, but suppose he tried it on with someone less able to defend themselves?"
Responding to Ms Goodwin's allegations, a spokesman for Mr Cameron said: "David Cameron was first made aware of this serious allegation yesterday. He was alarmed, shocked and concerned to learn of it and immediately informed the Cabinet Office.
"As is usual practice, the Cabinet Office will thoroughly investigate any complaint made."
Mrs May's official spokesman told a regular Westminster media briefing: "Of course this is something that we would be concerned about. We are looking at it, and as we have said, wherever an allegation has been made we will make sure it's treated with the utmost seriousness."
Ms Goodwin's story is the latest in a series of allegations of unwanted sexual advances at Westminster, with First Secretary of State Damian Green and international trade minister Mark Garnier facing inquiries over claims of inappropriate conduct.
Conservative former minister Anna Soubry described the alleged incident as "appalling", telling BBC Breakfast: "For a lot of women, it doesn't matter who you are, it doesn't matter how much bravado people think you have, this sort of assault - and it is an assault - is often deeply traumatic and we need to wake up to what it really is. And we need to take action when it is required.
"We have got to change the culture as well. And men should keep their hands to themselves."