Marinus van der Lubbe, 24, was beheaded after being convicted of setting fire to the Reichstag, an event Hitler used as a pretext to suspend civil liberties and establish a dictatorship.

But Van de Lubbe's conviction has been overturned by the federal prosecutor, Monika Harms, after a lawyer in Berlin alerted her to the fact that he had yet to be exonerated under a law passed in 1998. The law allowed pardons for people convicted of crimes under the Nazis, based on the concept that Nazi law "went against the basic ideas of justice".

But the exoneration is only symbolic and will not lead to compensation for Van de Lubbe's heirs.

Police arrested Van der Lubbe in the burning building, and he is said to have confessed that he started the fire in order to encourage a workers' uprising against the rise of the Nazis.

However, historians remain divided over the event. The Nazis said it was a communist plot and used the fire in propaganda. Most modern historians are in agreement that Van der Lubbe was involved in the fire, but whether he acted alone or with accomplices is still open to debate.

Following the attack in February 1933, which gutted the Reichstag and was a key event in the establishment of Nazi Germany, the Communist party was banned and Nazi opponents were brutally suppressed. In one night 1,500 communist functionaries were arrested.

When he was alerted to the news of the fire, which took place shortly after he had taken power, Adolf Hitler called it a "sign from heaven" that a communist putsch was about to be launched.

The day after the fire the Reichstag fire decree was signed into law, which led to the suspension of civil liberties and the banning of many newspapers and other publications hostile to the Nazis.

Van der Lubbe, who had moved to Germany to pursue his political beliefs, went on trial in Leipzig in 1933 along with four others, charged with arson and attempting to overthrow the government. But only Van der Lubbe was convicted. He was executed in January 1934.

The full pardon follows a decades-long legal process by Van der Lubbe's heirs to rehabilitate him.

In 1967 a Berlin court bizarrely changed the sentence to an eight-year prison term. In 1980 the same court lifted the sentence completely, a decision later reversed by the federal court. Then in 1981 a West German court overturned the conviction on the basis that Van der Lubbe was insane, but campaigners pushed for full state pardon arguing that he had been convicted by a Nazi court.

It took the 1998 law to make the full pardon possible but it is unclear why another 10 years went by before it was granted.