The declining popularity of the Who Wants to be a Millionaire? unsettled a second company in as many days yesterday when Eidos warned that a computer game based on the television quiz show was not selling as had been hoped.

The chief executive, Mike McGarvey, said the novelty of Millionaire appeared to be wearing off, and gamers were buying other formats such as a popular new game based on the Harry Potter books.

"There is only a finite amount of dollars in the marketplace and when a phenomenon like [Harry Potter] comes along it takes away from games like Millionaire," he said.

The downbeat assessment of Millionaire's popularity reflects similar sentiments expressed on Tuesday by Avesco, owner of the rights to the series. It said US viewers in particular had reassessed their priorities.

Eidos sold 2m units of its first Millionaire game when it was released in Britain and Germany last year but the follow-up is likely to ship just 1.2m, even though it is being introduced in eight countries.

Mr McGarvey said it was now hard to justify the release of a third game.

The Millionaire slowdown overshadowed an otherwise improved set of figures from the maker of the popular Tomb Raider series which earlier in the year was forced into a £52m rights issue to stabilise its balance sheet.

Operating losses narrowed from £20.5m to £19.6m for the six months to September 30, even though turnover slumped from £54.3m to £31m. Gross margins increased 4.6% to 60.5%. Shares were down 14% at 180.5p.

Mr McGarvey said that Eidos was benefiting from cost-cutting earlier in the year. He believed the company was in a position to ride the upturn in the fortunes of the games sector, which has been boosted by the release of a range of new consoles. Sony has recently released its PlayStation 2 console while Microsoft's eagerly awaited X-box goes on sale in Britain early next year.

"Next Christmas will be a blockbuster time for the industry," Mr McGarvey predicted.