The campaign, which was founded in 2010 by a group of American billionaires, including Bill and Melinda Gates and Warren Buffett, has been supported by 168 of the world's wealthiest people from 21 countries.

The Login couple are the founders of IT company Outfit7, which is best known for its globally successful app Talking Tom. The app was sold to Asian investors for US$1bn in January this year.

The couple, along with their children, are among the latest group of 14 new individuals and couples that joined The Giving Pledge, together with the likes of low-cost airline EasyJet founder Stelios Haji-Ioannou and Norwegian oil mogul Kjell Inge Rokke.

Samo and Iza Login wrote in their pledge that they dedicated all the money they received from the sale of Outfit7 to their Liechtenstein-based Login5 Foundation, which focuses on environmental projects.

"Not only are we pledging to spend most of our wealth on non-profit environmental projects - we're finally fortunate enough to be able to invest our time in these projects too," they wrote in a letter.