The cost of adjusting Britain's computers to cope with the turn of the century was yesterday put at £31 billion by the head of the British government organisation set up to tackle the so called "Millennium Bomb" problem.

It is the first time the cost of reprogramming Britain's computers so they can distinguish between dates in this century and the next has been priced officially.

Most "guesstimates" by consultants and computing services companies have put the cost at only about a third of the new figure calculated by Mr Robin Guenier, head of TaskForce 2000. This suggests that the seriousness of the timebomb threat is still underestimated by both businesses and the computer industry.