The tax came into force a year ago, and has seen most retailers charge around 10 cents for customers to purchase plastic bags.
Back in February 2015, Portugal had one of Europe’s worst rates of plastic consumption, with each inhabitant using an average of 466 bags a year.
That figure is now estimated to have dropped to below 50 bags.
The Government this week added that it expects to collect around 200,000 euros in taxes during the course of 2016 from the shopping bag tax.
According to the Environment Ministry, the previous Government had expected to rake in 40 million euros from the shopping bag tax last year, but only managed to collect 1.5 million euros as the vast majority of shoppers decided to use their own bags.
Ministerial officials are forecasting the use of plastic shopping bags to drop even further this year, and are only expecting limited revenue from the bag tax.
Research conducted by environmental watchdog Quercus at the beginning of last year on supermarkets found that people who shopped in supermarkets where plastic carrier bags were free, used more bags than necessary and did not fill them.
Quercus members came to this conclusion after they stood outside supermarkets observing shoppers’ bag habits for the study.
It was concluded that supermarkets that offered free bags encouraged waste as the majority of shoppers use more bags than necessary and only half fill them.
A spokesman from Pingo Doce supermarket, where shopping bags have had to be paid for since 2007, said that until the end of 2012, the use of plastic bags by consumers fell by 47 percent.
This decrease “enabled a reduction of 7,667 tonnes of plastic deposited in landfill and 15,265 less carbon dioxide emissions,” the Pingo Doce spokesman said.
Internationally, Ireland is the greenest when it comes to shopping bags. Back in 2002, a 15 cent fee was applied on all plastic bags and in three months, bag usage plummeted by 90 percent.