Women workers have been told to dye their hair blonde, wear revealing outfits and constantly reapply make-up, a study into workplace dress codes has found.
The "troubling" experiences suffered by female staff were unearthed by a parliamentary report into the case of a woman sacked for not wearing high heels.
More than 150,000 people signed a petition in support of London receptionist Nicola Thorp, who was sent home from work after refusing to wear high heels.
The 27-year-old arrived at finance company PwC to be told she had to wear shoes with a "2in to 4in heel" and when she refused and complained male colleagues were not asked to do the same, she was sent home without pay.
The Petitions Committee and Women and Equalities Committee said it became clear in the course of its inquiry that this was not an isolated incident.
"We heard from hundreds of women who told us about the pain and long-term damage caused by wearing high heels for long periods in the workplace, as well as from women who had been required to dye their hair blonde, to wear revealing outfits and to constantly reapply make-up.
"The Government has said that the existing law is clear, and that the dress code that prompted this petition is already unlawful. Nevertheless, discriminatory dress codes remain widespread.
"It is therefore clear that the existing law is not yet fully effective in protecting employees from discrimination at work. We call on the Government to review this area of the law and to ask Parliament to change it, if necessary, to make it more effective," said the report.
The Fawcett Society told the inquiry that requiring women to abide by gendered dress codes, often of a sexualised nature, sent out the message that their appearance was of more value than their skills, experience or voices.
"There have been statements from women expressing that being asked to look "sexy" in the workplace leads to the uncomfortable realisation that the business they work for is profiting from their bodies," said the campaign group, citing examples of women being asked when working in a casino to carry a make-up kit to be used whenever using the bathroom, and others being criticised for wearing loose clothing on a hot day.
"This also affects women at the top of public life as we have seen from headlines since Theresa May became Prime Minister.
"Having a society where it is normal to judge women in their professional life by their appearance and their shoes is not just ridiculous but demeans women who reach the top of their careers, and limits women's participation in politics."
Helen Jones, who chairs the Petitions Committee, said: "The Government has said that the way that Nicola Thorp was treated by her employer is against the law but that didn't stop her being sent home from work without pay.
"The Government must now accept that it has a responsibility to ensure that the law works in practice as well as in theory."
Ms Thorp said: "This may have started over a pair of high heels but what it has revealed about discrimination in the UK workplace is vital, as demonstrated by the hundreds of women who came forward.
"The current system favours the employer and is failing employees. It is crucial that the law is amended so that gender neutral dress codes become the norm."
TUC general secretary Frances O'Grady said: "Far too many employers are still stuck in the past when it comes to dress codes. It is unacceptable that in 2017 bosses are still forcing women to wear painful, inappropriate shoes and uniforms.
"But with employment tribunals costing up to £1,200, many women can't afford to challenge sexist policies. If ministers are serious about enforcing equality legislation then they should scrap tribunal fees immediately."
Sam Smethers, chief executive of The Fawcett Society, said: "Sexist dress codes which objectify women and make LGBT (lesbian, gay, bisexual, and transgender) employees feel excluded have no place in modern workplaces.
"Employers need to focus on what drives productivity and enables their staff to feel part of a team. It isn't a pair of high heels."
Equality and Human Rights Commission chief executive Rebecca Hilsenrath said: "In a modern business, it's simply wrong, and frankly antiquated, that any woman should be made to follow a dress code telling them how to look in a way that would never be asked of men.
"The height of my heels has no relevance to how good I am at my job. We are looking for test cases which will bring this issue to the national attention."
A Government spokesman said : "No employer should discriminate against workers on grounds of gender - it is unacceptable and is against the law.
"Dress codes must be reasonable and include equivalent requirements for both men and women.
"The Government Equalities Office will carefully consider this report and will work with its partners to make sure employers comply with the law."
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