A FAR-RIGHT activist was sentenced by a court in Amsterdam on Thursday to two months in prison for projecting a message onto the Anne Frank House museum alluding to an anti-semitic conspiracy theory.

Robert Wilson, a prominent member of the neonazi Goyim Defence League, was charged with insulting a group and inciting discrimination by projecting the words “Ann [sic] Frank invented the ballpoint pen” onto the side of the canal house where the Jewish teenager hid with her family during the Holocaust.

The text refers to a false claim that Ms Frank’s famed diary is a forgery.

The court wrote in its decision that “given the great symbolic significance of Anne Frank’s diary for the commemoration of the persecution of the Jews, this statement can be regarded as a form of Holocaust denial.”

Having already spent more than two months in pre-trial detention over the February incident, Mr Wilson has already served his sentence. The far-right activist was not in the courtroom for the verdict.

The judges ruled that Mr Wilson had projected the scrolling text from a van parked across the canal from the building in Amsterdam, which now houses the Anne Frank Museum. 

Mr Wilson denied the charges, claiming that he was in Amsterdam for a weekend getaway with his girlfriend and daughter and wasn’t even aware of where the Anne Frank House was.

Anne Frank kept a diary of life under German occupation during World War II but was arrested with her family in 1944 and sent to a Nazi concentration camp, where she died.

Several pages written with a ballpoint pen were found among her papers in the 1980s. 

That type of pen was not introduced in the Netherlands until after World War II and Holocaust deniers have claimed this proves the diary is fake. 

However, researchers have concluded that the pages were accidentally left in the diary in the 1960s.