Indian Narain Karthikeyan [Images] will stay on as an official Williams test driver next season, the Formula One team said on Thursday.

The former champions said in a statement at the Chinese Grand Prix that the Chennai driver would add "a vital element" of continuity to the test and development programme in their first year with new engine partner Toyota.

"Naturally as a racing driver, my first priority is to compete but I would far rather test with a leading team than accept a race seat that offered no real potential to learn and develop," Karthikeyan said.

"Williams is a team that exists only to race and I hope that whatever I can contribute to this ultimate objective will be valued by the team."

Karthikeyan joined the British-based team this year as a second test driver after a debut season with Toyota-powered Jordan that made him the first Indian to race and score points in Formula One.

He also has experience of using Bridgestone tyres, with the Japanese company becoming Formula One's sole supplier next season.

"His appointment is extremely popular within the team because he is hard working, conscientious and capable in the car," team boss Frank Williams said in a statement.

"It is also significant that Narain carries with him India's growing Formula One interests, which is very exciting."

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