Meanwhile, one in 10 said they had used a food bank to obtain free period products.
The situation is almost as desperate among older people who menstruate. A separate survey by Water Aid, which polled people who menstruate aged 14 to 50, revealed that nearly a quarter (24%) have struggled to afford period products in the last year.
Shockingly, Plan International UK found that 80% of young women who are struggling to afford period products have used loo roll as substitute. This is up by an eighth year-on-year. Others said they have used socks, pieces of fabric or newspapers when they have been unable to afford period products.
“It is devastating that so many girls and young people in the UK are unable to afford the period products they need, and that shockingly high numbers of them are forced to rely on toilet paper as a substitute," said Rose Caldwell of Plan International UK.
"Of even more concern, half of girls who struggle to afford period products report cutting back on food to be able to buy them, almost doubling compared to last year."
Caldwell added that as the cost-of-living crisis intensifies, even more young women are likely to find themselves in a similarly desperate situation.
She added: "We must commit to ensuring that everyone who needs them gets easy free access to products, receives timely education on periods and feels able to talk about the issues they face without fear of shame or stigma."
Several charities and organisations in the UK are working to eradicate period poverty and provide free period products, including Bloody Good Period, Freedom4Girls and Hey Girls. Free period products are also available in schools and at almost all food banks – you can find out where your nearest food bank is here.