The Czech constitutional court has upheld a controversial tax levied on solar power producers, which was introduced as a way of plugging the hold in the public deficit. However, an important motivation for the new tax was an attempt to curb an outbreak of speculation in the construction of solar farms, as they were taking advantage of state subsidies for green energy producers. The costs of the program were quickly becoming unsustainable. The tax came into effect at the end of 2010 and are set to remain in force until the end of 2013. The measure was seen as controversial as it applied to plants that were built beginning in 2009, when the owners could not have anticipated its introduction.