Anna Panczyk, chief executive of Grey London, has been on leave from the WPP creative agency since the middle of July amid speculation that she is to step down from the role.
A Grey London spokesperson confirmed Panczyk is "on leave" but would not comment further.
Separately, Grey London has told staff that jobs are at risk in a redundancy consultation because, like most agencies, it has been hit by the coronavirus downturn.
It is thought that at least 20 jobs are at risk because the agency is holding a consultation under employment rules; the number could be higher, although Grey London would not comment on that.
The spokesperson said: "Due to the current economic environment initiated by the Covid-19 global pandemic, Grey London is undergoing a redundancy process in order to future-proof its business and remain responsive to the evolving needs of its clients.
"Unfortunately, this process has become very common in our industry, nevertheless it remains a difficult one to go through. We will be doing our best to support our affected employees during these challenging times."
Grey London employed 281 staff before the crisis, according to its Campaign School Report 2020, which was published in April.
Panczyk took the helm of the London agency at the beginning of 2019, after previously serving as CEO of Grey Poland since 2015.
She replaced Leo Rayman, who moved to be global CEO of Grey Consulting in 2018.
While in Poland, Panczyk oversaw Grey Warsaw, shopper marketing arm Testardo, production division Grey Works, PR firm Cohn & Wolfe and Grey Digital.
Earlier in her career, she was CEO and chairman of independent agency Change Integrated and worked at Saatchi & Saatchi Poland.
If Panczyk leaves, it would be the latest in a series of senior departures from Grey London over the past year.
In November 2019, creative chairman Adrian Rossi was ousted after less than a year in the job.
Earlier in 2019, former chief creative officer Vicki Maguire quit to take the same position at Havas London, and chief strategy officer Matt Tanter decamped for Mother.
However, Grey has since filled both vacancies.
Laura Jordan Bambach, former CCO of Mr President, moved to the same job at Grey this year.
She works alongside Javier Campopiano, who was appointed creative chairman of the London agency alongside his role as Europe creative chief.
And at the start of 2020, Raquel Chicourel, M&C Saatchi’s former CSO, took over as Grey’s strategy chief.
Along with the staff departures, in 2019 Grey lost several accounts including McVitie’s, Jacob’s, Duracell, Lucozade and Marks & Spencer's clothing and home account. This year, however, the agency has picked up The Very Group and Aunt Bessie’s.
WPP previously warned that its creative agencies were under pressure globally, even before the coronavirus downturn, and said in April that it needed to make "some permanent headcount reductions" across the group.
In another notable change in Europe, Grey came under the leadership of sister shop Ogilvy in France in June, although Grey Paris remains an agency brand in its own right.