The government has announced an independent review of cigarette packaging in England, amid calls for action to discourage young smokers.
David Cameron appeared to distance himself from uniform packaging in July, saying further evidence was needed to show whether it would be effective.
But Public Health Minister Jane Ellison said it was now time to "examine the emerging evidence" on a policy shift.
Labour said immediate action was needed, "not another review".
In a Commons statement, Ms Ellison said standardised tobacco packaging would be brought in after the review if "we are satisfied that there are sufficient grounds to proceed, including public health benefit".
The review, led by paediatrician Sir Cyril Chantler, is set to focus on a pilot scheme in Australia, which became the first country to legislate for standardised packaging in 2011.
For Labour, shadow public health minister Luciana Berger demanded to know why the government was delaying the introduction of plain packaging "still further" having already held a consultation on the issue in 2012.
Opposition leader Ed Miliband added: "The government should have introduced plain packaging earlier this year - we want them to act swiftly, we want them to act now. We don't need another review.
"Every major public health expert agrees this would help the battle against cancer, against young people taking up smoking."
The government has never officially ruled out changes to cigarette packaging laws, but BBC political editor Nick Robinson said that private briefings from Downing Street had previously suggested the idea was "dead".
He said ministers were likely to have been defeated on Lords amendments to the Children and Families Bill, which enjoyed cross-party support, and would have given the government the power to regulate cigarette packaging.
Ms Ellison confirmed that the government would table its own amendment to the legislation, giving ministers the power to introduce regulations "quickly" when Sir Cyril's review is complete in March 2014 - if they decide to proceed with the policy.
'Rise in counterfeiting'
She rejected suggestions the rethink had been prompted by fears of defeat in the Lords, saying: "It's a year this weekend since the legislation was introduced in Australia. It's the right time to ask people to look at this.
"This is fundamentally about children's health. Two thirds of people start smoking when they're children and it's one of the most important public health issues we face in this country."
A study conducted in Australia found that smokers using standardised plain brown packets were 81% more likely to consider quitting.
Deputy Prime Minister Nick Clegg said the government had an "open mind" on the review, and "personally" he hoped it would show that plain packaging was effective.
But UKIP deputy leader Paul Nuttall accused Mr Cameron of "scandalously auctioning off the freedom and liberty of the British people for his own political ends, cheered on by the Labour Party".
Cigarette firm British American Tobacco (BAT), which owns brands including Benson & Hedges and Dunhill, said the Australian experiment had "failed" to achieve its public health objectives.
"The evidence shows that the introduction of plain packaging of tobacco products has coincided with an increase in illicit trade," leading to increased profits for "criminals selling black-market tobacco", it argued.
Labour has sought to link Conservative election chief Lynton Crosby's work as a consultant for the tobacco industry to delays in the policy, a claim which was rejected by David Cameron at the time the issue was put on hold in July.
The ban on images on packaging came into force in Australia on 1 January after a long-running legal battle between the former Labor government and the tobacco industry.
Manufacturers claimed the law was unconstitutional and infringed on their intellectual property rights by banning the use of brands and trademarks.
But they said they would comply after the legality of the measure was upheld by the country's highest court.
Cancer Research UK said a move to plain packaging would "save thousands of lives".
"Stopping cigarettes being marketed to children as a glamorous and desirable accessory is one of the greatest gifts we can give the next generation," it added.
More than 450 doctors, nurses and other healthcare professionals have signed an open letter saying they also "welcome" the move.
"Cigarette packs are now the key marketing tool employed by the tobacco industry to attract and retain customers," they wrote.
"There is no time to lose and Parliament must act now to protect children from the marketing tactics of the tobacco industry."
The Scottish government has said it is "still committed" to introducing standardised packaging, while New Zealand is also considering the move.