Plans for a law to make retailers charge 10p for a plastic carrier bag have been unveiled by an MSP at the Scottish Parliament.
Mike Pringle's proposed bill would levy a 10p charge per bag
Liberal Democrat Mike Pringle said money raised from the tax could fund environmental projects.
Peter Woodall, from the Carrier Bags Consortium, said the argument was the "the very worst case of junk science".
About one billion plastic bags are given away free in Scotland every year, but some stores now charge for them.
Mr Pringle, who unveiled his new bill on Monday, said plastic bags took a huge length of time to decompose in landfill sites and they made up 1% of the waste stream.
His Plastic Bags (Scotland) Bill sets out a plan which would force all shops to charge 10p per bag.
The Scottish Executive said it had not yet taken a view of the bill because any decision would have to be based on "sound evidence" of an environmental benefit.
The executive has commissioned its own study on the proposal for a bag levy. The findings, to be presented to parliament in the next few weeks, would be used to inform the decision-making process, a spokeswoman said.
The 10p tax collected by the retailers would then be passed to councils which would have to spend it on local environmental projects.
If the passage of the bill runs smoothly, then it could become law some time in 2007.
Mr Pringle believed there was evidence that where a levy had been made for carrier bags it was "remarkably successful".
Although some bags are reused, many are thrown away and sent to landfill sites where they can take decades to decompose.
Discarded bags have also been blamed for killing wildlife through suffocation or strangulation.
Home improvement giant B&Q last year started charging shoppers in Scotland 5p a time.
A plastic bag tax in the Republic of Ireland is said to have resulted in the number of bags changing hands being cut by about 90%.
B&Q started charging for its plastic bags in its Scottish stores last year
Companies involved in supplying plastic bags have argued that if shops try to avoid the levy by switching to alternatives such as paper bags, the environmental cost could be even higher.
Mr Woodall said: "Plastic bags do not degrade, and thank goodness for that. When things do degrade they produce CO2 and methane, the most potent green house gases.
"What will happen is that people will turn to buying paper and retailers will provide paper carrier bags which will degrade and there will be clouds of methane over Scotland."
He added that his industry had encouraged people to turn to carrier bags for life, but he had observed that Irish residents did not recycle carrier bags to the levels which were first thought.
"We have introduced a voluntary code which we hope Mr Pringle will accept rather than hitting the Scottish people over the head with a 1,400% tax on a product," said Mr Woodall.
Mr Pringle insisted that the Irish experience had been a financial and environmental success.
He said: "The country has taken in 41.5m Euros since this started and it costs 350,000 Euros per annum, so in fact it has been very successful with the money raised.
"The amount of plastic bags coming out of the waste stream is 95% in Ireland. Previous to this, 80% of carrier bags came from supermarkets.
"If you talk to the supermarket people now they will tell you that they don't give out plastic bags anymore, the only time they give the plastic bag out is to tourists who don't have a bag for life."
Friends of the Earth Scotland's head of research, Dr Dan Barlow, said Scotland was struggling to deal with rising waste.
He added: "The plastic bag levy in Ireland has been a great environmental success and gained widespread acceptance. Scotland's environment stands to benefit from a similar proposal."
The proposal has also won praise from the Scottish Green Party, the World Wildlife Fund Scotland and the Scottish Wildlife Trust.