The letters have been written by the Congress, DMK, Trinamool Congress and NCP.
The Islamophobic remarks against an MP on the floor of the Lok Sabha have emerged as a fresh rallying point for the Opposition in its battle against the BJP.
The comments by the ruling party's legislator Ramesh Bidhuri, which have sparked disgust, outrage and widespread condemnation since they were made on Thursday evening, have now prompted several letters to the Lok Sabha speaker, demanding immediate punitive action against the MP.
Four opposition parties have written to Speaker Om Birla on Friday. These include the Congress, DMK and the Trinamool Congress, which is significant because they are the three opposition parties with the most number of MPs in the Lok Sabha. The Congress' letter was released minutes after former party chief Rahul Gandhi met Bahujan Samaj Party MP Kunwar Danish Ali and posted photos of the meeting with a "mohabbat ki dukaan" (shop of love) message.
All the letters demanded that the matter of Mr Bidhuri's conduct and comments be referred to the Privileges Committee of parliament and immediate action be taken against him. The Opposition parties have also pointed to the "hypocrisy" of Congress' Leader in the Lok Sabha, Adhir Ranjan Chowdhury, being suspended for one insulting remark but no comparable action being taken against the BJP MP.
In his letter to the Speaker, Mr Chowdhury demanded punitive action against Mr Bidhuri for "using brazenly abusive and unparliamentary words against a member of a leading political party, Danish Ali, who also happens to be from the minority community".
"What is even more regrettable is the fact that this unprecedented, unfortunate and unsavoury incident has happened during the Special Session of the Parliament, that has been convened to commemorate 75 years of its history and that too, during the course of the discussion to mark the success of 'Mission Chandrayaan III'," the letter said.
"Considering the circumstances and the brazen violation of all norms and rules relating to the functioning of the House, it would only be appropriate to have the matter examined in detail by the Privileges Committee and punitive action taken against the errant Member, Ramesh Bidhuri," Mr Chowdhury wrote.
Similar letters were written by DMK leader Kanimozhi, Trinamool MP Aparupa Poddar and Nationalist Congress Party MP Supriya Sule.
"During the course of his speech Mr. Ramesh Bidhuri directed the most foul, abusive invectives against Mr. Kunwar Danish Ali which are part of the record of the Lok Sabha," Ms Kanimozhi said in her letter and demanded a privilege motion against the BJP MP.
All four parties are also part of Indian National Developmental Inclusive Alliance (INDIA) and several other members of the bloc also spoke in one voice against Mr Bidhuri's comments. Experts say the issue can help bring the bloc closer together especially in light of the speculation around seat-sharing disputes, the CPM's refusal to nominate a member to the coordination committee, and perceived differences over issues like the caste census.
Rahul Gandhi's outreach to a member of a party whose chief, Mayawati, has said she will remain non-aligned and attacked both the INDIA bloc and the NDA on multiple occasions, has also sparked a buzz in political circles.
The Aam Aadmi Party has also condemned the remarks and pointed to "no action" being taken against Mr Bidhuri while their MPs Sanjay Singh and Raghav Chadha remain suspended.
"We condemn these remarks. These remarks show the ideology of the party (BJP). When our MPs raise pertinent issues, they are suspended while no action is taken over such remarks," the party's chief national spokesperson Priyanka Kakkar told news agency PTI.
Mr Bidhuri's comments were also condemned by Samajwadi Party chief Akhilesh Yadav and National Conference leader Omar Abdullah, among others.
Speaker, BJP Action
Officials said Speaker Om Birla has taken "serious notice" of the communal slurs hurled by Ramesh Bidhuri' and warned him of "strict action" if he repeated such behaviour.
After outrage from the opposition and on social media, the BJP has sent a show-cause notice to the MP and asked him to explain his conduct within 15 days.
Defence Minister Rajnath Singh said in the Lok Sabha, "I express regret if the Opposition is hurt by the remarks made by the member." The Opposition parties, however, slammed him for offering a "half-hearted" apology.