ITV broadcaster Carlton's failed foray into digital television left it with a bill of £99m, as the company sought to draw a line under a "very difficult period".

The charge from the closure of ITV Digital and ITV Sport Channel was blamed, along with the severe downturn in the advertising market for pre-tax losses of £179.4m in the six months to March 31.

Advertising revenues tumbled 13 per cent on a like-for-like basis in the half-year as the economic slowdown meant many major brand owners cut back on marketing campaigns.

Turnover from Carlton's continuing operations fell seven per cent to £503.1m.

The pre-tax losses of £179.4m compare with even worse losses of £277.3m for the same period last year. Carlton, whose ITV franchises include Central and HTV, said last year's figure had been restated to reflect the closure of ITV Digital, which it co-owned with Granada.

It said the six months had been a very difficult period but that it was in a strong financial position with net debt of £38m. There were also signs the advertising market was starting to revive.

"The market appears to be firming through the summer months, even taking into account the expected fillip of the World Cup finals in June," the group said.

"Advertisers in most major categories are showing interest in renewed activity."

Carlton added that the closure of ITV Digital had increased its "financial flexibility" and it was now focused on growing its content and advertising sales businesses both in the UK and internationally.

But it would resist the Football League's claim for the £178.5m still outstanding to Nationwide League football clubs from the deal with ITV Digital.

"Having taken advice from leading counsel, Carlton and Granada believe the counter-claim has no legal basis whatsoever. Accordingly, it will be robustly defended and no provision has been made for it," Carlton said.

Carlton chief executive Gerry Murphy said the group was in talks with other free-to-air broadcasters about pulling together a new digital package that would include ITV channels.