Japan's Kazuki Nakajima, son of former F1 racer Satoru Nakajima, has been appointed as a Williams test driver.

The British-based Formula One team, who have Toyota engines next season, said in a statement on Wednesday that the 21-year-old would work alongside the team's other test driver, Indian Narain Karthikeyan.

Satoru Nakajima raced for Lotus and Tyrrell in the mid 1980s and early 1990s, with fourth place in the 1987 British Grand Prix and 1989 Australian Grand Prix his best results.

Kazuki competed in the Formula Three Euroseries this year and is a member of the Toyota young driver programme as well as a former Formula Toyota champion in Japan.

"Kazuki has consistently demonstrated his potential through karting and other junior Formulae," said team boss Frank Williams in the statement.

"Having assessed both his potential in the car and his aptitude out of it, we believe he has the necessary ingredients to graduate to Formula One in a testing role."

The team said he was expected to start testing before the end of the year.

The rules have changed for next year however, with teams agreeing to reduce testing while race weekends will also change format with a ban on teams using third cars in the Friday practice sessions.

Nakajima said he was delighted with his opportunity to become the first to graduate from the Toyota young driver programme to Formula One.

"For anyone with an interest in motor racing, Formula One is the ultimate objective," he said.

Former champions Williams have just finished their worst season in 30 years, scoring only 11 points and ending up eighth of the 11 teams.

They are now switching from Cosworth engines to Toyota power with a racing lineup of Germany's Nico Rosberg and Austrian veteran Alexander Wurz, who was test driver this year.