Shoppers could soon have to pay a minimum of 5p for plastic carrier bags as part of a crackdown on litter.
The Scottish Government is launching a three-month consultation this week on a range of proposals, including a ban on shops issuing free plastic bags.
The so-called "bag tax" is aimed at cutting the number used by up to 80% and is projected to raise £5m for charity.
A similar system introduced in Wales has cut carrier bag usage by between 60% and 80% in supermarkets.
However, Scottish Conservative environment spokesman Jamie McGrigor said the plan was impractical because of Scotland's wet climate.
He said: "Scotland is a very wet country, particularly in the west, and using other types of carrier bag just isn't practical in the way it is in other European countries.
"People will feel that, after spending a significant amount of money on their weekly shop, this is just another expense.
"I'm all for people reusing more sustainable bags, but my view is people who do should be handed incentives, rather than bringing punishment to those who do not."
Environment Secretary Richard Lochhead said: "Carrier bags are a highly visible aspect of litter. By reducing the amount being carelessly discarded, we can cut waste and its impact on our environment and economy.
"A small charge should also encourage us all to stop and think about what we discard and what can be re-used.
"This initiative will see retailers donating the proceeds to charitable good causes. It is hoped this could be up to £5m per year after retailers have covered their costs."
Green MSP Alison Johnstone said Scotland trails behind Wales and Northern Ireland in reducing bag waste and urged the SNP to explain why it waited almost a year to launch the consultation.
"The evidence from Wales is that a small charge is easy to implement and has a huge impact on shopper's behaviour, which can only be a good thing for litter in our towns and for our wildlife, seas and beaches," she said.