A tax on sugary drinks has not been ruled out as part of the Government's anti-obesity strategy, Downing Street has suggested.
Prime Minister David Cameron had been opposed to the move - which health campaigners led by TV chef Jamie Oliver are demanding.
But his official spokeswoman declined repeatedly to deny a report in the Times that the idea was back on the table amid mounting evidence it could cut sugar consumption.
The Department of Health insisted earlier it had "no plans" to implement the measure despite evidence it had been effective overseas and an appeal from a leading charity for it to be used to reduce cases of cancer.
In October, Number 10 said Mr Cameron believed there were "more effective ways of tackling this issue than putting a tax on sugar" but conceded he had not at that stage read a report from Public Health England saying a tax of 10% to 20% could work.
Pressed on the Times report however, his spokeswoman told reporters: "They are speculating on a Government strategy that is being worked on and that we will publish shortly. You will have to wait for the strategy."
"Work is ongoing on this. We are concerned about the issue here, the need for more to be done on this."
Cancer Research UK has called for a tax on sugary drinks for the first time in a bid to curb rising rates of cancer caused by people being overweight.
A study published in the British Medical Journal (BMJ) also shows that a sugary drinks tax in Mexico has led to a 12% reduction in sales and a 4% increase in the purchase of untaxed drinks one year after it came in.
From January 1 2014, Mexico implemented an excise tax of one peso (3p) per litre on sugar-sweetened beverages.
Researchers in the US and Mexico examined data from more than 6,200 Mexican households across 53 large cities, and discovered a drop in people consuming sugary drinks.
They found a rise in untaxed drinks sales, mainly due to more purchases of bottled plain water.
Gavin Partington, director-general of the British Soft Drinks Association, said: "The soft drinks tax in Mexico has reduced average calorie intake by just six calories a day and sales in France are back to pre-tax levels.
"By contrast, the soft drinks industry is taking practical steps to help consumers, through reformulation, smaller portion sizes and increased promotion of low and no-calorie options."