But the Culture Secretary, Chris Smith, said that he could not say when that date would be nor even when a decision would be made about it.

Most people will have to pay for new set-top boxes, TV sets and video recorders themselves but the government promised it would not force anyone to spend money who could not afford it.

An independent report commissioned by the government said most TV viewers could be reasonably expected to have made the switch to digital by 2013.

However, the government has decided that the switch-off will definitely not happen in the next five years.

The report by National Economic Research Associates (NERA) and Smith System Engineering revealed that the total cost to the nation of introducing digital TV could be as high as £16 billion.

Mr Smith said a consultation process would begin on Thursday to obtain opinions from the public and the TV industry about the change to digital.

Digital will allow viewers access to hundreds of channels

Digital TV offers more channels, clearer pictures, and ultimately interactive services.

It will also free up the analogue TV spectrum - the airwaves that currently broadcast TV pictures - to be used for other things, including mobile telephone calls and military communications.

Mr Smith could not say whether the top-level cost estimate of £16 billion could be offset by the possible revenue from selling off the analogue spectrum.

The NERA/Smith report makes several suggestions on how to bring in digital broadcasts. It says there would be considerable economic advantages in setting a date in advance - nearly 30% of households will have to buy new TV antennas, and many will need to replace video recorders.

The average household buys a replacement TV set every eight years, it adds.

Mr Smith said he thought it was up to TV retailers to "guide shoppers" about buying new TV sets in the next few years.

The report says the estimated gross costs of introducing digital could be:

• £1.1 billion for the transmission infrastructure,

• £6-£9 billion in costs to households - although this figure falls to £1-£2 billion when normal TV set replacement in taken into account,

• £6 billion in additional programme-making expenditure.

It will be left to market forces to bring digital equipment into the shops and for people to buy it, he said.