SOFIA (Reuters) – Bulgarian Prime Minister Boyko Borissov on Wednesday accused his political opponents of trying to undermine his government with the aim of blocking Bulgaria’s deeper integration into the European Union.

Borissov, 61, whose third government took office in 2017, has come under pressure this week due to an audio file published by some local media in which a voice similar to Borissov’s is heard making offensive remarks about the head of parliament and a deputy minister.

The voice on the recording also boasts about ordering an independent financial regulator to carry out a probe into a Bulgarian company.

Reuters could not verify the authenticity of the file.

Prosecutors have launched a probe into the audio, which refers to events of April, 2019, to check if it was acquired via illegal eavesdropping and whether it had been doctored.

In an emotional statement from the headquarters of his centre-right GERB party on Wednesday evening, Borissov said the audio had been doctored and called it a “manipulation”.

He also said that pictures of him published earlier on Wednesday on a local news website were “a setup”.

In one of the photos, Borissov is shown sleeping next to a gun on a bedside nightstand. Other pictures show only the nightstand filled with 500 euro notes and gold bars.

Reuters could not verify the authenticity of the pictures.

“Today our political opponents hit rock bottom,” Borissov said.

“Why now? Because July is an important month… Bulgaria, along with Croatia, is confidently on its path to join the banking union and the euro zone… They will not make me quit, nor will I stop.”

Bulgaria, one of the European Union’s poorest countries, hopes to join the ERM-2 ‘waiting room’ to the euro in July.

Borissov said entry in the banking union would ensure strict supervision over money flows and banks and would set the country, once the Soviet Union’s closest satellite, firmly in the Euro-Atlantic community.

Despite public anger over endemic corruption in the country, Borissov’s popularity has risen amid the coronavirus pandemic. Bulgaria has reported a relatively low 181 COVID-19 deaths, and two recent opinion polls showed his party ahead of its rivals.

Borissov said his opponents, including President Rumen Radev, the main opposition Socialist party, and other smaller political factions, were trying to rattle him and trigger early elections so the president could appoint a caretaker government.

General elections in Bulgaria are due next March.