Office workers and students may have to look for new ways to procrastinate, because one of the world’s most popular online games could soon be shut down. The makers of Scrabble have asked Facebook to remove Scrabulous, a popular version of the game, from its website.

In a move that has drawn protests from online fans of the game worldwide, the toymakers Hasbro and Mattel are pressuring the social networking site to ditch Scrabulous because, they argue, it infringes their copyright.

The Facebook application – which users can add to the personal profiles they create on the site – is hugely popular. About 600,000 users play the game online every day.

Thousands of players joined a “save Scrabulous” group on Facebook within hours of the news breaking. Many pointed out that they had bought the board game after playing the game online.

One student at a British university wrote: “Shameful as it is, I’ve headed out to buy a Scrabble set as a direct result of Scrabulous.”

Many, including the promoters of Scrabble tournaments, have credited Facebook with prompting a renaissance of the word game among young people. Another Facebook user, from London, wrote: “How ridiculous! Scrabulous had massively raised the profile of Scrabble, rendering it actually quite cool (where it was once seen as rather geeky).”

Some Facebook users posted the contact details of the toymakers on a message board, urging fans to inundate them with complaints in an effort to get the decision overturned.

Scrabulous is one of Facebook’s ten most popular applications. According to the Scrabulous website it has 594,924 daily users – about a quarter of the number that have signed up to play it.

The request to remove the game came from both Hasbro and Mattel, as ownership of the Scrabble trademark is split between the two companies. Hasbro owns rights to the game in the US and Canada, and Mattel has rights for the rest of the world.

In a statement, Mattel said: “Letters have been sent to Facebook in the United States regarding the Scrabulous application. Mattel values its intellectual property and actively protects its brands and trademarks.

“As Mattel owns the rights to the Scrabble trademark outside the United States and Canada, we are currently reviewing our position regarding other countries.”

Yesterday users could still play the game online. Facebook told news agencies that it had no comment to make on the manufacturers’ request.

The Scrabulous add-on was not built by Facebook but was created for the site by Rajat and Jayant Agarwalla, software developers based in Calcutta.

Admitting that the pair were earning $25,000 (£13,000) a month from advertising on the application, Jayant Agarwalla told Fortune magazine: “They sent a notice to Facebook about two weeks ago. The lawyers are working on it.”

Stewart Holden, from the Association of British Scrabble Players, said: “We are very keen to see anything which gets young people playing Scrabble for the first time. Nothing has done that over the past five years better than the Scrabulous application on Facebook. Many of our members use it.

“We understand the legal reasons for it [the request], but the effect the site has had on the game is undeniable. It would be a shame if that had to come to an end.”

Applications such as Scrabulous are regarded widely as one of the key reasons for the popularity of Facebook. The site is thought to have about 39 million members worldwide, and accounts for 1 per cent of all internet traffic.

The application has helped to spawn many “Scrabble cheat” websites for those players desperate to win at all costs. Websites such as Scrabblesolver provide users with an almost guaranteed victory. The sites can work out the best moves by allowing players to see every possible word combination with the letters they have in their hand.

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