Italy's prime minister, Silvio Berlusconi, today threatened to block the workings of the European Union unless commissioners and their spokespeople were gagged and prevented from speaking out on "any subject".

His astonishing demand came after commission spokesman Dennis Abbott, from Britain, disclosed that the body would ask the Italian government for clarification of an incident on Sunday in which migrants trying to reach Italy were turned back to Libya.

Abbott said he was "surprised, really surprised" by the Italian prime minister's attack. "For days we have been saying that the commission is not criticising any EU state over its handling of immigration," he said.

Berlusconi said Abbott's words had been used by his opponents for their own ends. "It is a problem I shall bring to the table of the next council of the heads of state and government, and my position will be precise and decisive," he said. "We shall no longer vote, blocking in effect the workings of the European council [of ministers], unless it is decided that no European commissioner and no spokesperson may intervene publicly on any subject."

Under Berlusconi's plan only the president and his or her spokesperson would be authorised to speak for the commission. Those commissioners who defied the ban would be "dismissed for once and all".

Last Friday it emerged that Berlusconi was suing a French magazine for an article on scandals involving him and was also seeking damages of €1m (£0.9m) from an Italian newspaper for demanding answers to questions about his private life. The same day his family's newspaper accused the editor of the Catholic church's daily of involvement in an affair allegedly involving homosexuality and harassment.