The number of children who have taken up smoking has risen by 50,000 in just one year, research suggests.
About 207,000 children aged 11 to 15 started to smoke in 2011, a sharp rise from 157,000 in 2010, Cancer Research UK said.
The charity said the figure equates to 567 children taking up the habit each day.
Almost one in three (27%) of under-16s have tried smoking at least once, a study by the charity found.
It urged the Government to commit to putting all cigarettes in plain standardised packs.
Last April, the Government launched a consultation on plans to introduce mandatory standardised packaging for tobacco products.
Health campaigners have welcomed the proposal, but opponents claimed it would lead to increased smuggling and job losses.
Information generated by the consultation, which closed in August, is still being analysed by health officials.
Sarah Woolnough, executive director of policy and information at Cancer Research UK, said: "With such a large number of youngsters starting to smoke every year, urgent action is needed to tackle the devastation caused by tobacco.
"Replacing slick, brightly-coloured packs that appeal to children with standard packs displaying prominent health warnings is a vital part of efforts to protect health.
"Reducing the appeal of cigarettes with plain, standardised packs will give millions of children one less reason to start smoking.
"These figures underline the importance of sustained action to discourage young people from starting.
"Smoking kills and is responsible for at least 14 different types of cancer. Standardised packaging is popular with the public and will help protect children.
"We urge the Government to show their commitment to health and introduce plain, standardised packs as soon as possible."
In December, Australia became the first country in the world to put all tobacco products in standardised packs.
Cigarette packets and other products are all sold in a standardised colour, with only the brand name and graphic warnings visible.