Former Union minister Yashwant Sinha, a bitter critic of Prime Minister Narendra Modi regime, joined Trinamul Congress on Saturday, days ahead of the high-octane West Bengal Assembly polls.

Sinha, a senior BJP leader during the Atal Bihari Vajpayee government's rule, told reporters it was call of the hour to ensure TMC wins the Assembly elections with a thumping majority which would herald the defeat of Modi government in 2024 Lok Sabha polls and save the country.

"The tipping point was the attack (in Nandigram) on Mamata Banerjee. When I spoke to her today, she described the incident to me." he said, adding that he had .had 45-minute conversation with her before joining her party.

"This government can do anything to win the election. The attack on Mamata Ji made me decide that I want to work with her," he said about the March 10 incident.

Sinha, who served in the cabinet of former Prime Minister Atal Bihari Vajpayee, had quit the saffron party in 2018 after having serious differences with the present party leadership. His son Jayant Sinha is the BJP MP from Hazaribagh in Jharkhand.

The octagenarian leader had campaigned for TMC in the 2019 Lok Sabha polls.

Speaking after joining TMC at its office here, the bureaucrat-turned-politician, made a scathing attack on Modi and Union Home minister Amit Shah, observing that democracy in the country was under threat under them. "The strength of the democracy lies in the robustness of its institutions, and all the institutions have been weakened systematically," Sinha said.

"The country is faced with strange situation. The values and principles we gave so much importance, the founding principles of our Republic are not being followed. The farmers of the country are sitting near Delhi for months but the government doesn't care. The ruling party has only one objective - win elections by any means," he said.

The senior politician pledged support to West Bengal Chief Minister Mamata Banerjee in her fight against the BJP. "TMC will win the polls by thumping majority. But, we have to increase the victory to another level.

"(Gopal Krishna) Gokhale had famously said, 'What Bengal thinks today India thinks tomorrow'. Bengal should herald changes. The win of TMC in West Bengal Assembly polls will ring in changes in 2024 general elections and defeat them (Modi-Shah) led BJP," Sinha said.

Observing that the BJP led by Atal Behari Vajpayee was vastly different from the saffron party today, Sinha said, "Atal ji believed in consensus. Now Modi and Shah believe in crushing opposite opinion. Atal ji believed in taking people along, but the present BJP regime believes in conquering people.

"Atal ji believed in coalition, now coalition partners are leaving BJP one after another."

Sinha said migrant labourers were forced to come back home by foot during the coronavirus-triggered lockdown while education, healthcare are also going through a rough phase but the government does not seem to be bothered.

The veteran politician observed it is a serious fight today, not merely to win elections but to save the Republic

Sinha recalled during Kandahar hijack of Air India plane, when TMC was the coalition partner of the Vajpayee government, Banerjee had volunteered at the cabinet meeting to go and meet the hijackers to secure release of hostages "as she is not afraid of her life."

Sinha's joining Trinamul Congress might not help it win votes, but his utterances against the BJP could lend weight to TMC's offensive against the saffron party in the high- voltage Bengal polls.

"We welcome Yashwant Sinha to our party. His participation would strengthen our fight against the BJP in the coming elections," TMC Lok Sabha party leader Sudip Bandopadhyay said earlier.

Sinha was two-time finance minister, once in the Chandra Sekhar cabinet in 1990 and then again in the Vajpayee cabinet. He also held the portfolio of the external affairs ministry in the Vajpayee cabinet.

He served as the Principal Secretary to then Bihar Chief Minister Karpoori Thakur in 1977.

Influenced by Loknayak Jayaprakash Narayan, Sinha, had resigned from the IAS in 1984 and plunged into politics.