By Johannes Birkebaek

COPENHAGEN (Reuters) -Denmark has dropped charges against a former defence minister and a former spy chief over allegations of leaks of classified information, Danish prosecutors said on Wednesday, after court rulings meant top secret evidence would have to become public.

Former minister Claus Hjort Frederiksen and former head of the Danish Defence Intelligence Service Lars Findsen had been charged under a rarely used section of the penal code that carries a maximum sentence of 12 years in prison.

Both men have denied any wrongdoing since they were charged.

The charges have been dropped after a series of verdicts in the Supreme Court of Denmark decided that the trial against the former minister would not happen behind closed doors - and therefore classified information could not be shown in court.

"The classified information is crucial to the cases. Without the ability to present them in court, the prosecution has no chance to meet the burden of proof," the Prosecution Authority said in the statement.

The precise charges have not been made public, but Frederiksen suggested to local media they were based on public statements made he made about a secret surveillance agreement between Denmark and the U.S. National Security Agency.

(Reporting by Johannes Birkebaek;Editing by Alison Williams)