Ms Josephs, who was formerly the director general of the Cabinet Office Covid Taskforce, has today posted a statement on Twitter admitting attending the gathering.
The revelation comes following a week of staunch criticism of Downing Street for repeatedly holding drinks and gatherings while the country was in lockdown.
In a statement following the revelation, Labour’s Councillor Fox wrote: “Kate has made a statement today about a gathering that happened in the Cabinet Office last year. I have discussed this in person today with Kate on a one-to-one and she has said sorry.
"To be honest, I need to express my deep disappointment – people will rightly feel angry and let down. I get that completely. After everything that Sheffield has been through during the pandemic, this is news that we did not want to receive.
"Over the last year, Kate’s been an asset to our city, and she is working tirelessly for Sheffield and its people. Our residents will understandably have questions and concerns, and we await the findings of the investigation.”
The Star has contacted Councillor Fox for further comment.
Meanwhile, Councillor Douglas Johnson for the Green Party said: “The thing is, we can’t really talk about it. She’s put this out, and that’s all there is for now.
When asked if this Councillor Josephs should resign, Councillor Johnson said: "There’s no reason she should resign.” He declined to comment further, saying to wait for the investigation to end.