SOFIA, Bulgaria—Bulgarian prosecutors are alleging that former Interior Minister Tsvetan Tsvetanov was responsible for illegally wiretapping political opponents during his term.

Tsvetanov, who is running for Parliament in May 12 general elections and therefore has immunity, has denied any wrongdoing in a growing scandal some have dubbed "Bulgaria's Watergate."

The Sofia City Prosecutor's Office has already charged four senior police officials in the wiretapping case. On Tuesday, it said Tsvetanov was responsible for their actions.

Tsvetanov is managing the election campaign of his center-right party, Citizens for Bulgaria's European Development. He was a member of the Cabinet that quit in February amid social unrest in this nation of 7.3 million.

Last week, the former agriculture minister accused Tsvetanov of illegally wiretapping everyone in that previous Cabinet, but offered no proof.