"While we welcome Michael Schumacher back to Formula One, the fact is any form of in-season circuit testing is strictly prohibited, a regulation clearly laid out by the FIA and adhered to by all of the teams, " said Williams in a statement.

CNN: Motorsport: Williams block Schu testing bid

In March 1986, Williams suffered spinal cord injuries in a car accident after leaving the Paul Ricard Circuit in France, where he had been watching testing.

BBC: honours F1 team boss Williams

At the Barcelona circuit, which hosts the Spanish Grand Prix, many cars set lap times in testing this month that were quicker than pole position for the 2012 race.

CNN: New F1 season, new thrills?

But a rule change, announced on Friday, will allow one day of testing at a non-F1 circuit if the substitute driver has not raced in F1 for two seasons.

BBC: F1 amends in-season testing rule after Schumacher row

The Briton, who has been testing at the Circuit de Catalunya this week, says he is feeling much more at home back in Europe.

CNN: Hamilton bullish about return to Europe