Congress leader P Chidambaram has accused the Centre of using investigating agencies to target his son and his friends, in order to "silence" his voice against the government.

"All I will say is, I shall continue to speak and write," the veteran leader said in a statement in Chennai on Tuesday as the CBI launched searches at several places linked to the former finance minister and his son Karti over alleged favours granted in foreign investment clearance to a firm, INX Media, in 2007.

Chidambaram said FIPB approval was granted in "hundreds of cases". Each case was processed according to law and approval was granted or refused in accordance with the recommendations of the FIPB consisting of five secretaries to the Government of India, he said.

The five secretaries who constitute the FIPB, the officials of the FIPB secretariat and the competent authority in each case are the public officials, Chidambaram said, adding there was no allegation against any of them. "There is no allegation against me," he added.

"The government, using the CBI and other agencies, is targeting my son and his friends...The government's aim is to silence my voice and stop me from writing, as it has tried to do in the cases of leaders of opposition parties, journalists, columnists, NGOs and civil society organisations," the former finance minister said.

Asked about the raids, Chidambaram said: "You should have called your CBI friends... Should I stop writing (against the government)? I mean... (this is) absolute nonsense."

The agency had registered a case regarding alleged irregularities in granting the Foreign Investment Promotion Board (FIPB) clearance to INX Media, run by its directors Indrani Mukerjea and Peter Mukerjea, in 2007 when Chidambaram was the finance minister.

Chidambaram, a staunch critic of the Narendra Modi-led BJP regime, had said that his voice against the Centre cannot be silenced by launching cases against him or his son Karti, also a Congress leader.

(with PTI inputs)