A £250 million raid on the licence fee to pay for the costs of digital switchover, forcing the BBC into programme cutbacks, may be a waste of money, the National Audit Office has warned.

The body called on the Government to re-examine its figures for the plan which will see the analogue signal television switched off by 2012.

Households still need to convert or replace up to 26 million analogue televisions, including secondary sets, if they are to receive signals after switchover, the NAO report found.

With the rise of Freeview, 85 per cent of households now have at least one digitally-enabled set. The Government estimates that the total conversion costs for consumers will be £3.8 billion.

The BBC has set aside £800 million to pay the costs of switchover, money removed from programming, which has prompted thousands of job cuts under a reduced licence fee.

The BBC agreed to fund a Government scheme to help the disabled and elderly convert to digital. But take-up from the first region to convert, in Cumbria, suggests the demand has been massively over-stated.

The NAO said: “Our re-run of the cost model for the help scheme suggests that the funding requirement in the licence fee settlement to 2012-13 would reduce by some £250 million.”

Ministers should re-assess whether “all the sums due to be raised though the licence fee for the help scheme are still required.”

Edward Leigh MP, Chairman of the Committee of Public Accounts, said: “Nearly a third of the population has no idea what to do to continue watching television after the analogue switch off.

“At the same time, in the first seven months of 2007, 45 per cent of all televisions sold were still analogue. This is a recipe for confusion. It certainly suggests that a lot of screens will go blank after switchover.”

He added: “The Government needs to improve its estimate of just how much the help scheme is going to cost. It should collect from licence-fee payers only what it needs.”

Don Foster, Liberal Democrat Media spokesman, said: “This report adds weight to the view that the Government massively overestimated the number of people who need help making the transition to digital.

“Progress has been made, but it will come as little comfort to the hundreds of BBC employees who lost their jobs following the Government’s tight licence fee settlement.” He called on the Government to return unspent cash to the licence-fee payer.

A spokesman for the BBC Trust said: “We will continue to monitor the help scheme to ensure the money is spent efficiently. It could be too early to assess the take-up for the scheme.”

Jeremy Hunt, Shadow Culture Secretary, said: “Its time the Government got to the bottom of why they have failed to get the message out there both on switchover in general and the assistance scheme in particular.

“We need know what they will do if there is a significant under-spend on the assistance scheme – this is public money and they need to say where it will be spend if it’s not needed for its original purpose.”

The Department for Culture, Media and Sport must decide whether unspent money ring-fenced for switchover, could be returned to the BBC after 2012.

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