Soon after its leader and former union minister RPN Singh quit the party and joined the BJP, the Congress on Tuesday said it is fighting an ideological battle in which only those with courage can carry on and not cowards.

Congress spokesperson Gourav Vallabh said Singh was ''not fully committed" towards the party's ideology and that is why he left this fight midway to join the saffron party.

Another Congress spokesperson Supriya Shrinate said the Congress is fighting against the arrogance of the current government and its agencies.

"To fight this battle for truth and ideals, one needs strength and courage and cowards cannot fight this battle," Shrinate said.

Former union minister RPN Singh resigned from the party and joined the BJP, saying he wants to contribute to the nation's development while reposing faith in PM Narendra Modi.

He announced on Twitter that he was starting his new political journey.

Singh is also the party in-charge of Jharkhand affairs where the Congress is in power along with the JMM.

Amba Prasad, a Congress MLA in Jharkhand also accused Singh of destabilising the Congress-JMM government in the state.

"For more than a year, RPN Singh ji was trying to overthrow the Congress-JMM government of Jharkhand by colluding with the BJP. The party leadership was also constantly warned about this. Every true Congressman of Jharkhand is happy with his going to the BJP," Prasad said in a tweet in Hindi.

Singh was only yesterday included in the list of the party's 30 star campaigners for the first phase of the assembly election in Uttar Pradesh.

He is yet another high-profile leader to desert the Congress after Jyotiraditya Scindia and Jitin Prasada quit and joined the BJP earlier.

Shrinate said the battle of ideology that the Congress is putting up across the country, particularly in Uttar Pradesh, requires fighting the government's resources and agencies.

"For a battle as strongly pitched as this one, you have to fight it with courage and you have to fight it with a lot of dedication. I don't think this is meant for the coward," she said.

Vallabh while giving best wishes to Singh said had he been fully committed to the Congress ideology, he would not have joined the party which he has been fighting against.

Congress leaders felt that his quitting would not make a difference to the party in the upcoming assembly polls and its battle of ideology against the BJP.

"Today, at a time, we are celebrating the formation of our great Republic, I begin a new chapter in my political journey. Jai Hind," Singh said on Twitter.

RPN Singh in a letter to Congress President Sonia Gandhi, said, "I hereby tender my resignation from the primary membership of the Congress party with immediate effect."

"I thank you for providing me an opportunity to serve the nation, the people and the party," he also said.

"This is a new beginning for me and I look forward to my contribution to nation-building under the visionary leadership and guidance of the Honourable Prime Minister Shri Narendra Modi, BJP President Shri JP Nadda ji & Honourable Home Minister Amit Shah ji," he later said in a tweet.

Sources said he was upset with the party leadership over his close associates being denied party tickets in Uttar Pradesh.

Singh is a former MP from Kushinagar in Uttar Pradesh and has served as Union Minister of State for Home Affairs.

He hails from Padrauna and is a scion of the royal family there.

RPN Singh has earlier contested and represented the Padrauna assembly constituency. He may contest from the seat once again.

He had also defeated Swami Prasad Mourya, who recently quit the BJP and joined the Samajwadi Party, from the Kushinagar Lok Sabha seat in 2009.