Monica Lennon has written to Chancellor Rishi Sunak urging him to exempt all reusable menstrual supplies from VAT.
The ‘tampon tax’ was abolished from menstrual products such as pads, tampons and menstrual cups in the UK in January last year.
However, VAT still applies to reusable items such as period pants as they are classed as clothing.
Ms Lennon, who secured universal free access to period products, has warned rising costs are now putting women and girls who menstruate at a disadvantage.
Anyone in Scotland who needs free period products can already access them following a change in the law. Schools, colleges and universities must also provide them.
Yet one in four UK women and girls are struggling to afford period products, according to research carried out by the charity WaterAid.
Ms Lennon said the UK Government was “misguided” in treating items such as period pants as luxury goods.
The Chancellor recently told the MSP there were “no plans to change the rate of VAT charged on period pants”.
Ahead of Menstrual Hygiene Awareness Day on Saturday, Ms Lennon said: “It’s upsetting that a quarter of women and girls in the UK who menstruate said they or their family are struggling to afford period products.
“We cannot allow the cost-of-living crisis to strip a generation of young girls of their dignity and opportunities to learn.
“The UK is still one of the wealthiest countries in the world, with the Chancellor himself making the list of the nation’s richest people. We have more billionaires than ever before. However, we also have more women and girls going without period products.
“Reusable period pants are kinder to the planet than disposable period products, and the Government should be doing all it can to encourage the switch to more eco-friendly alternatives.”
Menstrual Hygiene Day is a global event that aims to break the taboos and end the stigma surrounding menstruation, and to raise the awareness of the challenges regarding access to sanitary products and education about menstruation.
Those who require period products in Scotland can find out where they are available for free using the PickUpMyPeriod app.