In-game item sales to hit $4.8bn by 2016

And a third of the money will come from tablet-based gamers.

A new report from Juniper Research says sales of in-game items will rise from $2.1 billion in 2011 to $4.8 billion in 2016.

It believes the growing acceptance of virtual items and the whole freemium habit will encourage a big spike in usage among casual social gamers. At present much of the activity comes from a more hardcore demographic.

Juniper also claims that in-game purchases will play its part in reducing piracy as the game is typically downloaded for free, and any purchases must be verified via the developers' server.

Report author Charlotte Miller said: "An increasing number of games developers are finding the in-game purchase model attractive simply because it provides easy answers.

"Their piracy rate will drop and the game will see more downloads. However, while some games may generate significant revenues from in-game items, the model doesn't work with all games and developers have to tread a fine line between encouraging purchases and appearing to be exploitative."