More than 137,700 girls have missed school in the last year because they couldn't afford sanitary products, a survey has found.
The findings emerged in a report of 500 girls aged 10 to 18, which showed 7 per cent have been forced to skip school during their period.
Of those girls, the average has missed five days of school during the last year.
In an attempt to avoid such a situation, 6 per cent of parents admit they have been so desperate to equip their daughters with sanitary protection they have resorted to stealing on the occasions they couldn't afford to buy them.
More than a fifth of parents said they had gone without something themselves so they had enough money to meet their daughter's needs. The studies among girls and parents were carried out by OnePoll.com
Aileen Nathan, associate director of sanitary pad manufacturer Always, which conducted the research, said: "These findings show that period poverty is a widespread problem amongst school girls in the UK.
"We're pledging an estimated 5 million pads to schools to help those girls achieve their full potential."
Alesha Dixon, an Always ambassador, said: "The more awareness we can raise about this issue, the more we can help to remove the shame girls feel in talking about it.
"Puberty is a hard enough time to navigate without feeling embarrassed about not being able to afford essential sanitary products and no girl today should experience that."
A quarter of all school girls have at some point been forced to use tissues or cotton wool, or double up on underwear, as they have not had the appropriate protection.
As well as having to throw underwear away due to lack of supplies - 13 per cent - more worryingly 11 per cent of girls were found to be putting their health at risk by using products such as tampons for far longer periods than recommended because they did not have a replacement.
And nine in 10 girls know they're not alone - as they have been asked by a friend for a pad or tampon because she couldn't afford to buy her own.
Of the 500 parents polled, a fifth said they have struggled to afford sanitary protection for their daughter, and one in 10 have been forced to send her to school without pads or tampons, knowing she needed them.
Always also spoke to 545 of the nation's teachers about 'period poverty' via We Are Futures, to find out how period poverty was affecting children in schools.
They discovered more than half of teachers are aware of some children being unable to afford protection for their period, and four in 10 have resorted to supplying students with pads or tampons from their own handbags to try and help.
Luckily for students, almost half of teachers acknowledge the girls in their class will be too embarrassed to talk about what they need, but the same percentage have intuitively identified those in need of help.
And school staff are frustrated about the issue, with two in five feeling like they are failing their girls by not being able to provide them with a long-term solution, and a third feel angry because they think they should be doing more as a school.
This is highlighted by the fact 85 per cent of schoolgirls have no idea how or where they can get free sanitary protection.
And nine in 10 parents say their daughter's school has not communicated with them about period poverty in any way.
Always will donate a pad to a school girl in need for every pack of pads bought in shops.
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