New Delhi | A Congress MP on Monday demanded that the Ministry of External Affairs put up a strong case against designated terrorist Gurpatwant Singh Pannun with authorities in the United States.

Raising the issue in the Lok Sabha, Ravneet Singh claimed that no action has been taken against him by the US despite the Indian government writing to the American authorities 26 times.

Singh said he failed to understand the requirement for "absolute proof" raised by the US authorities against Pannun, who heads the pro-Khalistan banned outfit 'Sikhs for Justice'.

Dubbing Pannun as a "clown", the Congress MP said despite India writing to the Canadian authorities, the Royal Canadian Mounted Police took no action resulting in the downing of Air India 'Kanishka' which led to the death of over 300 people.

He described the bombing of the aircraft as the "biggest mass murder" in Canadian history.

Singh added that Pannun has now threatened to blow up the Parliament building and warned passengers boarding Air India flights.

Pannun has been designated as a terrorist by the Union home ministry under the anti-terror law UAPA.