A Prague court on Friday dropped abuse of power charges against a top aide to former Czech prime minister Petr Necas, whose centre-right government collapsed over a bribery and spy scandal in 2013.

Jana Necasova, formerly Nagyova, was charged with abusing military intelligence in 2012 to spy on Necas's then wife Radka.

At the time, it emerged that Nagyova and Necas were having an affair. The scandal that ensued toppled Necas's government and sparked a drawn-out political crisis.

The court, which ruled that Necasova's actions did not constitute a crime, also acquitted three military intelligence officers charged with having ordered the spying.

Necas divorced Radka, his wife of more than 25 years with whom he has four children, in August 2013 to marry Nagyova just a month later.

The scandal triggered a political firestorm in the EU country of 10.5 million people and led to a snap election in October 2013.

The leftwing Social Democrats won the vote and formed a three-party coalition government with the centrist ANO movement of billionaire Andrej Babis and the smaller Christian Democrats party.