The right-wing Democrats for Strong Bulgaria (DSB) party asked for the interrogation of former prosecutor-general Nikola Filchev who, according to the party, appointed Alexei Petrov as special services' undercover agent in 2000.

DSB's Atanas Atanasov, who in 2000 was head of the now former National Security Service (NSS) under the government of DSB leader Ivan Kostov, told reporters that Filchev had to be arrested and interrogated as a result of the findings of police operation Octopus, carried out on February 10 2010.

The operation resulted in the arrest of 14 people, including Alexei Petrov, a former adviser to the State Agency for National Security (SANS). On February 12 2010 Sofia City Court ruled that all of the detainees remained under arrest. On February 18 the court is to decide whether all be set free or kept under arrest for the duration of the legal proceedings against them.

The group targeted by the operation was involved in serious economic crimes, influence peddling, racketeering, procuring, prostitution, money laundering and tax evasion over the past 10 years.

What caused public outcry was the fact that Petrov, often described by Bulgarian media as one of the most influential people in the country's criminal world was a secret agent of the special services for years and as such had access to classified information.

The Petrov row backfired on almost all parties in Parliament as it turned out that Petrov has been working as undercover agent under the last three governments.

According to Atanasov, Petrov was appointed as secret agent of the NSS in 2000 on Filchev's request. Atanasov was quoted by local media as saying that he had no real power over the appointment of Petrov as a NSS agent, despite the fact that he was head of the NSS at the time.

Atanasov said that he has never read any of Petrov's reports in his capacity as NSS secret agent infiltrated in Bulgaria's criminal world.

So far Filchev has not made any comment on the issue, despite accusations from all sides that he appointed and protected Petrov over the years.

Filchev was appointed as Bulgaria's ambassador to Kazakhstan in February 2006, after his seven-year term as prosecutor-general expired and he was succeeded by Boris Velchev.

In June 2008 he asked to be relieved of his duties as ambassador and returned to Bulgaria and went back to being law professor in one of Sofia's universities. He has been away from the public eye ever since.

In an interview with Bulgarian-language Dnevnik daily on February 15 2010 Filchev called Atanasov’s words "a lie" and denied having asked for the appointment of Petrov at the NSS.

He said that NSS’ undercover agents were appointed by the respective interior minister on the request of the NSS leadership. In 2000 interior minister was Emanuil Yordanov and NSS head was Atanasov.

"While I was prosecutor-general, NSS’ secret agents never had any direct contact with prosecutors. Everything was moved by Interior Ministry" he said. "As far as I known Petrov never did anything for the Prosecutor-General’s Office while I was prosecutor-general" Filchev noted.

"It is not difficult to open the NSS records at the State Agency for National Security and see when and by whom Petrov was appointed" Filchev said and noted that Petrov has been appointed by Atanasov who was no speculating with the issue.