Bosses who force employees to wear high heels as part of their work dress should reconsider their policy, the TUC union body has said.
Several "big City institutions and upmarket shops" were the worst offenders, it added, urging them to permit "healthy and safe footwear".
Slip-on shoes and high heels can lead to long-term foot problems, it said, especially with prolonged standing.
Workers should be able to wear footwear appropriate to their job, the TUC said.
"Heels may look glamorous on the catwalks and on Hollywood stars, but they're not appropriate for day-to-day work wear," said TUC general secretary Brendan Barber
"These dress codes - apart from being blatantly sexist - can lead to long-term foot and back problems as women are forced to stand or walk around in high heels or ill-fitting footwear."
He added that "instead of worrying about what their staff look like", employers should concentrate on the impact that the wrong shoes and standing for prolonged periods can have.
"We were surprised how many times we found that employers' dress codes did not permit the wearing of comfortable sensible footwear by women," Mr Barber said.
"Employers should look at encouraging their staff to come to work in comfortable shoes and, where possible, provide the option of sitting."
The TUC's report, Working Feet and Footwear, also looked at issues including firms providing slip-resistant shoes when needed.
And where there was the possibility of standing on nails or other sharp objects, bosses must ensure that staff wore shoes with puncture-resistant soles, the TUC added.