Skype has unveiled a test version of its latest Skype 4.0 upgrade, offering improved video and options to help users better manage calls.

The VoIP provider is keen to promote its video calling service which it says accounts for around 28 per cent of all Skype call minutes.

Video calls can now be launched with one click and can be accompanied by one-click IM chat sessions. Video calls also start in a much larger screen by default.

"This is one of the most fundamental changes we've made in the one and a half year history of the company," said Mike Bartlett, director of Windows product management at Skype.

Bartlett stressed that Skype 4.0 is still very much in beta form and that the company is looking to user feedback over the coming months to shape the final product.

"When you change something dramatically, it can be quite difficult to get used to for your user base. This is an unfinished piece of work at the moment."

Version 4.0 has also been designed to accommodate Skype-certified hardware, allowing the application automatically to recognise new devices such as headphones.

"Over the years, we've added a lot of richness and functionality to Skype. It's no longer just a little piece of software for making free calls," said Bartlett.