Rangamma, 12, works in a quarry smashing stones in Bangalore, India. The back-breaking work is normally reserved for criminals doing hard labour. ((Plan Canada))

Lack of education for girls hampers their earning potential, costing the world's poorest countries billions of dollars a year in lost revenue, according to a new report released Tuesday in Toronto.

"Study after study confirms that if young women are economically active, their country's economy grows and all members of their family benefit," said Rosemary McCarney, president and CEO of the Canadian arm of Plan International, which released the report.

"Investing in girls delivers a higher return than any other investment made in a country's development, and yet this isn't happening. That's a huge loss for everyone."

The third annual Because I Am A Girl report found that countries with high levels of institutional discrimination against girls and women were also the least developed.

Just a one per cent rise in the number of girls attending secondary school boosts a country's annual per capita income growth by 0.3 per cent, the report said.

In the case of Kenya, $3 billion could be added to the economy if the country educated its girls to secondary school level.

However, in tough economic times, girls in poor countries are the first to be pulled out of school as families struggle to pay for books, uniforms and other costs. The move tends to consign them to a life of servitude and poverty.

Plan called for a global 10-point action plan, including providing girls with education, better jobs, access to land or property and leadership opportunities.

To coincide with the report release, Olympic freestyle skier Jennifer Heil joined Plan in Toronto on Tuesday to launch a nationwide campaign to enlist Canadian girls in raising awareness about the importance of girls' rights around the world.

Plan, formerly Foster Parents Plan, is an international development agency founded in 1937 whose focus is justice for children in developing countries.