"With immediate effect all our female colleagues can wear plain flat shoes," Portico said.
The announcement follows revelations by a London-based receptionist Nicola Thorp who was told to wear shoes with a "2in to 4in heel" when she arrived for work at finance company PwC last December.
Thorp, 27, refused and was sent home, leading to her setting up a petition calling for the law on the dress code to be changed, signed by over 50,000 people.
"I was expected to do a nine-hour shift on my feet escorting clients to meeting rooms. I said 'I just won't be able to do that in heels'... I said 'if you can give me a reason as to why wearing flats would impair me to do my job today, then fair enough', but they couldn't," she said.
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The company said the dress code issue involving Thorp at its central London office was "not a PwC policy".
Portico, a firm which hires reception staff for corporate offices like PwC, later said it was "committed to being an inclusive and equal opportunities employer" and actively embraced "diversity and inclusion within all our policies".
"We are therefore making it very clear that with immediate effect, all our female colleagues can wear plain flat shoes or plain court shoes as they prefer," said Managing director Simon Pratt.