A whole new political controversy has erupted over the 1984 anti Sikh riots case. Earlier in the day, the Delhi High Court sentenced Congress leader for life imprisonment over the charges of conspiracy to commit murder.

While BJP leaders have taken the occasion to target the Madhya Pradesh CM designate Kamal Nath on the day of the swearing-in ceremony, Congress urged all the parties not to politicise the issue.

Union Finance Minister and senior BJP leader Arun Jaitley said that Sajjan Kumar’s conviction by the Delhi High Court is a delayed vindication of Justice. Taking to Twitter, he wrote, "The Congress and the Gandhi family legacy will continue to pay for the sins of 1984 riots.”

“For many of us who are witnesses [of the riots], it was perhaps the worst kind of genocide that we ever saw,” Jaitley said.

"Congress governments in that period repeatedly indulged in cover-up exercises. The cover-ups are now being defeated. Sajjan Kumar was a symbol of 1984 anti-Sikh riots. The legacy of 1984 anti-Sikh riots hangs around the neck of Congress and Gandhi family.”

Taking a jibe at Kamal Nath, he added; "It is ironic that this order comes on the day when another person who Sikhs consider guilty” is taking charge as the chief minister of a state.

Kamal Nath was questioned by the Nanavati Commission for his alleged role in the riots but had been absolved of involvement for lack of evidence.

BJP spokesperson Sambit Patra slammed Congress President Rahul Gandhi and asked for his resignation." A man involved in anti-Sikh riots has been made the MP CM. Mr Rahul Gandhi must expel him from the party", Patra also lashed out at Kamal Nath.

BJP national information and technology chief Amit Malviya in a tweet, took a dig at Kamal Nath in light of the recent High Court verdict on the 1984 Anti-Sikh riots. "Ironical that on the day Sajjan Kumar gets life sentence for his role in state sponsored Sikh genocide of 1984, another man named by an eyewitness, an IE reporter, for leading a mob that killed two Sikhs in Gurudwara Rakabganj will be sworn in as Congress CM of Madhya Pradesh," he said.

Delhi BJP leader Tejinder Pal Singh Bagga started his hunger strike at Tilak Nagar in west Delhi where several families affected in the 1984 anti-Sikh riots live.

Protesting the Congress's move in selecting Nath for the chief minister's post, he said, "I am sitting on an indefinite hunger strike against Rahul Gandhi's decision to nominate him as CM. He (Nath) is the same person who was involved in the riots against Sikhs in Delhi."

He said his hunger strike will continue till Nath is replaced by someone else as chief minister of Madhya Pradesh.

Several BJP leaders are supporting Bagga's protest.

BJP leader and Leader of Opposition in the Delhi Assembly Vijender Gupta said the Congress has "hurt" Sikh sentiments by appointing Nath as chief minister.

Meanwhile, leaders from the Aam Aadmi Party, the BJP and the Punjab Congress Committee Monday welcomed the conviction of Sajjan Kumar.

President of the Punjab Pradesh Congress Committee, Sunil Kumar Jakhar, said the party has been clear that whoever was involved in the riots should be brought to justice.

"Yes, justice has been delayed but delivered finally. Nobody is above law and anyone who is involved in such a heinous crime should be brought to justice," the Congress MP told reporters outside Parliament.

He also said Congress leader Kamal Nath's name never figured in the list of those involved in the riots.

The riots, in which thousands of Sikhs were killed, broke out after the assassination of prime minister Indira Gandhi by her Sikh bodyguards on October 31, 1984.

Delhi Chief Minister Arvind Kejriwal welcomed the verdict convicting the 73-year-old Congress leader.

"It has been a very long and painful wait for innocent victims who were murdered by those in power. Nobody involved in any riot should be allowed to escape no matter how powerful the individual maybe," Kejriwal said on Twitter.

His AAP colleague and Supreme Court lawyer H S Phoolka also welcomed the judgment and thanked everyone for their support and help.

Shiromani Akali Dal (SAD) leader and Delhi MLA, Majinder Singh Sirsa, said the judgment has "given us big satisfaction".

"It took 34 long years for justice because Congress was in power. The case was closed but it was opened again by the Nanavati commission. This case was kept closed by Congress for so long," he said.

Union Minister Hardeep Singh Puri, outside Parliament, welcomed the judgment, saying "justice has been delayed but served".

Reacting to the verdict, Union minister Harsimrat Badal said; "I want to thank PM Narendra Modi that on Akali Dal's request in 2015 he set up an SIT to probe 1984 massacre. It's a historic judgement. Wheels of justice have finally moved".

"It is Sajjan Kumar today, it will be Jagdish Tytler tomorrow then Kamal Nath and eventually the Gandhi family", she added.

Amid widespread criticism, Congress leaders said that the case should not be politicised and the law should take its own course.

"It should not be linked to the political atmosphere prevailing in the country. The law should take its course, there are appeals," senior Congress leader Abhishek Manu Singhvi said.

There have been verdicts in the past where people have been found guilty, while others have been absolved, he told reporters.

"This should not be politicised and political benefit should not be derived from this," Singhvi said.

Kumar does not hold a position of power in the party, his colleague, senior Congress leader Kapil Sibal, added.

"What decision has been taken by the court is a legal process. We have seen how cover up is going on in the Sohrabuddin case... and what about Justice Loya's death?" he asked, referring to the Sohrabuddin Sheikh encounter case and the suspicious death of Justice B H Loya who was hearing the case.

"Don't give it a political colour as it is a court decision," he told reporters.

Sibal also brought up the issue of the 2002 riots in Gujarat and alleged that a number of BJP leaders were named in the cases.

"Charity should begin at home," he said.

Sunil Kumar Jakhar, president of the Punjab Pradesh Congress Committee, said the party has been clear that whoever was involved in the riots should be brought to justice.

"Yes, justice has been delayed but delivered finally. Nobody is above law and anyone who is involved in such a heinous crime should be brought to justice," the Congress MP told reporters outside Parliament.

Party leader Ghulam Nabi Azad refused to comment when asked for his reaction.

The riots broke out after the assassination of prime minister Indira Gandhi by her Sikh bodyguards on October 31, 1984.