The move is a response to BMW's dominance of the first two rounds of the championship at Magny Cours and Monza.
The weight reduction will be in force from this weekend's third round of the championship at Silverstone, meaning that BMW's rear-wheel-drive 320is will have a 50kg disadvantage on their rivals.
Alfa Romeo driver James Thompson, the only non-BMW driver to win a race this season, welcomed the move. Thompson told Autosport-Atlas: "It is not healthy for a championship to be dominated by one manufacturer. BMW were walking away from us.
"Monza is historically a circuit for front-wheel-drive cars but we were overrun by BMWs. At that rate BMW were going to get the first six place in the drivers' championship. This reduction will make us more competitive."
This is the first intervention of the Bureau, established to take quick decisions about technical and sporting matters. It has been expected that the Bureau would wait until after this weekend's round of the championship, but it felt the performance differential was too big.
This intervention was passed under by Article 83 of the FIA WTCC Sporting Regulations. It enables the Bureau to adjust the minimum weight of the cars at any time during the season in order to keep performances balanced.
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