Why do women have to pay GST on tampons and menstrual pads? That's what some Canadian women are asking the government, saying the tax amounts to gender discrimination, period.

The group "No Tax on Tampons" argues it's inherently unfair that there is no GST on items considered essential to daily life, such as groceries and kids' clothes, but there is a tax on tampons. They've now launched an online petition asking the federal government to change the rules.

"Menstruation products are not things we choose to use," the group's spokesperson Jill Piebiak tells CTVNews.ca.

Eyeglasses and incontinence products are free from the GST, and that makes sense to Piebiak: Canadians can't be productive in society without them.

"But the same is true of menstruation products. We need these to live a normal, public life," she says.

While some might argue there are other things subject to the GST that could also be considered essential, such as toothpaste and toilet paper, Piebiak says the tax is inherently discriminatory because it affects a very specific half of the population, based on their reproductive systems.

"It puts an unfair tax burden on people with a particular biology," she adds.

This is not the first time Canadian women have protested the tax on tampons.; in fact, there's been anger on the issue pretty much since the GST was introduced back in 1991.

At least two private member's bills have been brought before the House of Commons in the past, demanding that feminine hygiene products be exempt from the tax, including one in 2004, from former NDP MP Judy Wasylycia-Leis.

Irene Mathyssen, NDP for London-Fanshawe has now taken up the cause, introducing Bill C-282, An Act to amend the Excise Tax Act (feminine hygiene products) in 2011 and again in 2013.

Mathyssen says it's ridiculous that things like wedding cakes and cocktail cherries are exempt from the GST, but the government can still earn millions each year from sales of an item that women have no choice about buying.

"It means women are paying $30 million in taxes for a product that is for women, absolutely essential," she says.

Other similar bills have died on the floor, but this time organizers have been able to harness the power of social media. Their online petition has already earned close to 45,000 signatures in less than three weeks.

The petition offers support for Bill C-282 and sends an email to the prime minister, the minister of revenue and the minister on the status of women to let them know that Canadians are fed up with the tax.

Piebiak says she thinks most Canadians don't even realize women have to pay this tax, but instantly want to do something about it when they find out.

"It's an issue where, as soon as you become aware of it, it's something you're right away frustrated with," she says.

The group's goal is to have Bill C-282 debated before Parliament falls ahead of an expected fall election. It's unclear whether the federal government is interested in such a debate.

David Barnaby, a spokesperson with the Department of Finance, which sets policy on taxes, told CTVNews.ca that the department does not, as a rule, comment on policy proposals.

While this issue moves forward here in Canada, campaigns protesting similar taxes are underway in the United Kingdom and Australia, where organizers call the taxes "a bloody outrage." Mathyssen says it seems this is an issue that stirs up anger, the world over.

"This is one of those things that brings women together and gets them fighting mad," she said. "This is just so unfair and I'm glad that women are responding."