Flexible working could lead to women losing out in the workplace, former prime minister Theresa May has warned as she pointed out that “out of sight can be out of mind”.

Mrs May said the issue of caring responsibilities was one that “constantly” came up during her time as minister for women and equalities, adding that a lot of women today find themselves “sandwiched between” childcare responsibilities as well as caring for elderly parents.

She said she found that often managers at a very senior level in business would recognise the importance of flexible working, but that middle management did not like it.

In a conversation with Australian ex-premier Julia Gillard to mark International Women’s Day, Mrs May said: “It was middle management that found it most difficult and I think it was because often for middle management, presence in the office was their way of judging your output, rather than actually having to judge the output on its own sake.

“So if you’re in the office you were working. The fact that you might actually be flexibly working, be at home, and produce as much and as good an output as in the office they found difficult to comprehend.

“What has happened of course in the pandemic is that’s turned it all on its head because now everybody has found that they can, unless they’re doing a very practical physical job, they’re able to work at home.”

She said flexible working “can be done”, adding: “So hopefully more managers will recognise now, and I think we’ll see flexibility being offered for all in a way that it wasn’t previously.

“Bu there’s a potential negative here for women I think which we have to beware, which is that if more women use that than men, and so more of the women are not physically present in offices, being seen by senior management, able to have the conversations around the coffee machine, then there’s a potential that they will lose out.”

Mrs May told a story about a woman she met in Australia who timed her arrival every Monday morning so that she would share the lift with the chief executive.

“She waited by the lifts until she saw the chief executive walk in, and she pressed the lift button, and lo and behold they always went up in the lift together and her career blossomed.

“But that’s about women actually seeing the opportunities to make the most of that physical presence.

“And I think there’s a danger if we see a lot of women rightfully doing the flexible working and seeing that as a way to better manage their responsibilities, but perhaps forgetting that out of sight can be out of mind,” she said.

The conversation was a Global Institute for Women’s Leadership event at King’s College London.