32% of those who paid spent their money on subscriptions.
British gamers spent £280m playing online casual games in 2009 says the UK National Gamers Survey Report.
Similar studies carried out in other countries revealed that French players spent £220m and Germans £440m over the same period.
The survey estimated that there are 13.3m Britains playing on various game portals but only 2.4m pay to play - an average of £117 per person per year.
Gamers in the UK were also said to have spent £170m on mobile games in 2009.
The survey was carried out by TNS and Gamesindustry.com.
"In the future all games are going to be social," John Vechey, founder of casual game developer PopCap, told BBC News. "Every game you have will be interactive in some way."
PopCap specialises in games that can be played on social networks or online in short bursts.
Mr Vechey believes that the interactive nature of online games is a return to tradition when families played games and competed against each other at home.
Short and sweet
One of PopCap's biggest hits is Bejeweled, which challenges players to line up and match as many gems as possible in 60 seconds as they fall from the top of the screen.
The Facebook version, Bejeweled Blitz, launched in 2009 and registered 25m players within 12 months.
"Bejeweled is a good time stealer," says player Darren Haynes.
"It is completely addictive - mainly because each game only lasts for one minute. I found myself saying "just one more game" and before I knew it ... 3am."
Mr Haynes compared the game with arcade classic Tetris.
"We were somewhat surprised by Bejeweled's success but we put a lot of work in," said Mr Vechey.
"It only took two months to make but you have to keep working on it. A game isn't done when you release it. It's important to keep the core simple and fun."
Constant tweaks like re-setting the leader boards have helped to keep the game fresh for existing players, he believes.
PopCap is now looking to expand more into the mobile games market, and is launching a game called Plants vs Zombies that has proved a popular download with PC players.
"The iPhone is a great customer experience - you can spend 30 hours on an iPhone," says Mr Vechey.