Cigarettes sold in plain, sludge-green packets are less appealing and make smokers "prioritise quitting", a new study from Australia suggests, but the Department of Health still insists it is waiting for "the impact to be measured" that plain packaging works.
Last year Australia became the first country in the world to sell tobacco products in plain, standardised packs.
Researchers examining the early impact of the scheme found that smokers were "less satisfied" when their tobacco came in the plain packs.
Earlier this month the British Government announced that plans to go ahead with plain packaging in England would be postponed until ministers had had a chance to assess the impact of the scheme in Australia.
Ministers faced fury from health campaigners who said that brightly coloured packages are one of the last marketing ploys that tobacco companies use to lure people, especially children, to their products.
Following the announcement to put the plans on ice, Downing Street was forced to deny that the Tories' elections strategist Lynton Crosby was responsible for the delay to plain packaging.
Crosby's links with alcohol and tobacco firms have been called into question by some MPs.
Crosby, who was brought in last year after masterminding Boris Johnson's re-election as London mayor, has reportedly advised David Cameron to "get the barnacles off the boat" and concentrate on the core concerns of voters such as the economy.
In April last year, the Government launched a consultation on plans to introduce mandatory standardised packaging for tobacco products.
But after more than a year, officials still have not made a decision.
Australia introduced the policy in December last year. Cigarette packs and other tobacco products are all sold in a standardised brown colour, with only the brand name and graphic warnings visible.
Research into the scheme, published in the online journal BMJ Open, was conducted to find out the effects the policy was having in the early stages.
The authors interviewed 536 cigarette smokers in the Australian state of Victoria during November 2012 when plain packs were already available - 72.3% of them smoked cigarettes from plain packs while the remainder were still using branded packs with smaller health warnings.
They found that, compared with branded pack smokers, smokers using plain packs were 66% more likely to think their cigarettes were poorer quality than a year ago and they were 70% more likely to say they found them less satisfying. They were also 81% more likely to have thought about quitting at least once a day during the previous week.
"Overall, the introductory effects we observed are consistent with the broad objectives of the plain packaging legislation," the authors said. "We await further research to examine more durable effects on smokers and any effects on youth."
Kate Alley, Cancer Research UK's tobacco policy manager, said: "This new evidence from Australia confirms what we already know, selling cigarettes in standardised packs makes smoking less appealing and encourages smokers to quit. When cigarettes aren't disguised by flashy packaging and carefully crafted branding, smokers see them for what they are - a lethal product which kills half of its long term users.
"100,000 people die of a smoking-related illness and 207,000 children take up smoking every year in the UK.
85% of the British public want Government action to reduce the number of children who smoke. The Government should stop stalling and introduce standardised packs in the UK as soon as possible. Any delay will cost lives."
Deborah Arnott, chief executive of health charity Ash, said: "This new study from Australia adds valuable new evidence that standard packs increase smokers' desire to quit which is closely linked to successful quitting.
"This adds to the strong evidence we already have from the UK Government commissioned review of the evidence which clearly showed that plain, standardised cigarette packs are less attractive to children. Cameron's line that he wants to wait for the evidence is just a fudge so he can kick this into the long grass. Every day the Government dithers hundreds of children take up smoking, many of whom will become shackled to a lifelong addiction leading to life changing diseases and premature death."
A Department of Health spokeswoman said they were still waiting for yet more evidence.
"We take very seriously the potential for standardised packaging to reduce smoking rates, but in light of the differing views, we have decided to wait until the emerging impact of the decision in Australia can be measured, and then we will make a decision in England.
"This decision is an important one and whilst we keep it under review, we'll be continuing to implement our existing plan to reduce smoking rates through ending the display of tobacco in all shops, running national behaviour change campaigns to encourage smokers to quit and through supporting local authorities to provide effective stop smoking services."