Lib Dem activists have called on the leadership to consider introducing a "plastic bag tax" despite warnings that it could drive up carbon emissions.
The Lib Dems say 17 billion plastic bags are given out annually
Party leaders had wanted a deposit scheme, with customers charged for disposable shopping bags and refunded when they are returned.
But members backed an amendment calling for consideration of a levy on plastic bags, as used in Ireland since 2002.
Lib Dem MP Jo Swinson said packaging cost the average family £470 a year.
She claimed research showed that using bags made from materials other than plastic could lead to more carbon emissions.
A container which could transport 1.5 million plastic bags, could only carry just over 50,000 paper bags, which would push up road haulage emissions.
However, a deposit scheme, rather than penalising shoppers for using plastic bags, would encourage their reuse, she said.
The party also voted for large supermarkets to provide waste points for customers to dump unwanted packaging.
Lib Dems say total waste produced in the UK has increased by 21% since 1997, with householders sending five million tonnes of packaging to landfill sites every year.
A Lib Dem survey of UK supermarkets found more than 17 billion plastic bags are given away each year.
During a debate at the party's annual conference in Brighton, Martin Tod, a former marketing director for a packaged goods company, said the UK over-wraps a wide range of products.
Mr Tod, also the Lib Dem parliamentary candidate for Winchester, gave the example of toothpaste he used from a tube he had designed in his previous job.
"It came in a carton and I and my colleagues had actually designed that tube so that it didn't need one..." he said.
"In many cases, the same products are sold with less packaging in other countries."
The conference also backed a motion calling for a new national body with prosecution powers to tackle "large scale producers of excess packaging".
The debate comes as a Guardian/ICM opinion poll suggests Lib Dem leader Sir Menzies Campbell is now more popular than Conservative leader David Cameron.
The poll will come as a major shot in the arm for Sir Menzies, who has faced continued questions about his leadership during this week's conference.
The man most often tipped to succeed him, home affairs spokesman Nick Clegg, told a fringe meeting he would "probably" bid for the leadership in the future.
But he ruled out a challenge to Sir Menzies, urging the party to support him and "put two fingers up" at its critics.
"At a time when Sir Ming is being attacked with barely disguised ageism... the only response is to pull together, put up two fingers and say, don't you dare push us around," said Mr Clegg.
The Lib Dems are hoping the policies debated this week - which have focused around the environment and "fairer" taxation - will give them a distinctive platform on which to fight the next general election - and avoid the traditional third party "squeeze".
The party will also debate constitutional reform - including lowering the voting age to 16, a bill of rights, a referendum on a written constitution, greater use of citizens' juries and the introduction of proportional representation for Westminster elections.
There will also be emergency motions on guns and gangs - and provision for Britain's armed forces.