"The red flag is the only one that can block the Hindutva onslaught," Sitaram Yechury said.

The Communist movement in India will turn 100 years next year and to mark the occasion the Communist Party of India (Marxist) commenced year-long celebrations with a meeting in Kolkata on Thursday where the party called for a no-holds barred battle against Hindutva and the BJP-RSS attempts to polarise the country on communal lines.

"The red flag is the only one that can block the Hindutva onslaught," CPM general secretary Sitaram Yechury told the meeting at Netaji Indoor Stadium. "Our slogan 'inquilab zindabad' is the only one that can confront Hindutva communalism in the country and save it and change it into a better, socialist country," he said.

The CPM's West Bengal unit marked the event with a significant break from the past. It inducted into the party's key decision making body a number of young leaders, all under 55, and retired at least four top brass who were around 70 years.

Laying a roadmap to 2024, Mr Yechury called on all like-minded parties to come together to take on the "rightist" forces. He also hit out at BJP president Amit Shah for his comments that every illegal migrant in the country will be sent home before the next Lok Sabha polls in 2024.

"He has the right to say what he likes. But we are denied the right. If we speak our mind, we will be called tukde tukde gang or urban naxals," Mr Yechury said.

"He has said he will throw out all infiltrators by 2024. Who are the infiltrators? How will we know? Whoever they say. And the UAPA amendments turn topsy-turvy the country's basic tenet that you are innocent till proven guilty," he said.

The Communist celebration was not without controversy. While the CPM believes that the Communist Party of India was founded on October 17, 1920 at Tashkent in Uzbekistan, its parent CPI sticks to a December 1925 birth day, at Kanpur in Uttar Pradesh.

The CPM broke away from the parent CPI in 1964 over CPI's so-called "closeness" to the Congress. Today, the CPM is drawing closer to the Congress than the CPI. In his speech, Mr Yechury called for like-minded parties to come together against the BJP for the upcoming elections.

The CPM and the Congress are showing all signs of drawing closer ahead of 2021. On October 2, for the first time ever, top leaders from the CPM went to the Pradesh Congress office for a meeting with top Congress leaders.

According to sources, there was some talk of inviting the state Congress to Netaji Indoor stadium but it did not materialise.

However, with the elections to 107 civic bodies coming up early next year, the two parties could come together sooner rather than later.

"We have a bright future, we are the only party who can bring about a change for the better," said a 32-year-old party worker who had gathered at the Netaji Indoor rally.

The silver lining for the party which once ruled three states in the country but is now in power only in one was the turn out at the meeting. Netaji Indoor Stadium has a seating capacity of about 15,000 people. There were at least an equal number of people outside the stadium, said a senior party worker, adding, had it not rained, there could be many more.