He is considering withdrawing his pledge to donate 52 works to the reconstructed Barberini Museum in Potsdam.
According to the German press, Plattner is concerned that private collectors and museums will no longer be free to sell individual works and - if the new laws are adopted - will consider moving his art out of Germany to the US.
Plattner's intervention comes after heavyweight Contemporary artists, including Gerhard Richter and Georg Baselitz, threatened to withdraw their loaned artworks from German museums.
The granddaughter of the great German Expressionist Max Beckmann has also said she may remove works on loan to museums from her family, fearing their 'detainment' in Germany.
Many auctioneers, dealers, trade bodies, galleries, collectors and artists are opposing the law change which "will severely restrict trade in Germany, which will inevitably have a detrimental effect on prices across the entire market". They are encouraging their customers to sign a petition opposing the controversial amendments to the German Cultural Property and Heritage Protection Law.
The proposed changes to the law were put forward by German minister of culture Monika Grütters in July.
The headline element of the proposals is that all cultural objects valued at €300,000 or more and older than 70 years will require an export licence if they are sold to a foreign buyer.
However, the draft law also asks, in the case of a legal dispute, that the owners of 'cultural goods' with a value of at least €2500 provide proof of the item's provenance for the previous 20 years. In the case of any item classed as 'of archaeological value', the value is €100.
The protesters believe this due diligence clause - and the bureaucracy it will create - is an unrealistic demand which will severely damage the legitimate market.