BBC websites cost 50 per cent more than budgeted, it emerged today, because it did not properly account for the costs of supporting its family of sites ranging from online news to the 606 sports comment pages.

The BBC was meant to spend £74.2 million last year, but in fact spent £110 million, at a time when commercial rivals are already complaining about the impact the public broadcaster is having on their businesses.

Uncovered by the BBC Trust, the Corporation’s regulator, the budget overspill was described by that body as “a serious breach” that stems from “a lack of financial accountability” in the way BBC websites are run.

In contrast, it is estimated all British newspapers, from the Financial Times to local titles, spend around £200 million on their websites, meaning that the BBC invests more than half the total expenditure they make.

Technology spending to support BBC websites was wrongly allocated elsewhere, in an error that amounted to £13.8 million; while employee costs were £11.1 million higher because people who were working to support bbc.co.uk’s activities were being placed on other budgets.

As a result of the problems, the BBC Trust decided that it would adopt “a cautious approach to new investment”. The BBC wants to increase its online spending by £39 million next year to invest in better technology, and spend further unspecified sums on controversial local video news services and education sites for six to 10-year-olds.

If all were approved, that would take the BBC’s online budget to well over £150 million, although Patricia Hodgson, a member of the BBC Trust said that the local news and education services would be subject to a “public value test” to see if they unfairly impacted on commercial rivals. Cash-strapped regional newspaper owners are particularly unhappy that BBC could take online readers away from their sites with a generously funded video news.

A statement from the BBC’s management said that the budgeting problems were “regrettable and we recognise the need to address this” and stemmed from the fact that employees who worked on bbc.co.uk were spread around across the Corporation.

Elsewhere, the BBC Trust largely gave the bbc.co.uk site a positive review, describing it as an “excellent service that is highly valued” by the public, although “more needs to be done to ensure that all parts of bbc.co.uk are distinctive” from commercial offerings.

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