Some opposition members had complained about Mr Thakur shooting video of their protests in the Well on July 24 and AAP member Bhagwant Mann had written a letter in this regard to the Speaker.
While stating that nothing has come to her notice, Ms Mahajan said if someone had done so, then it is condemnable. "If you have done it, then you have to tender an apology (to the House)," she said.
Thereafter, Mr Thakur gave a statement and expressed regret.
"Mobile se agar kisi ko aapattee hai to ... mein khed vyakt karta hoon (If someone has objections to (my) mobile, then I express my regret)," Mr Thakur said amid noisy protests by opposition members.
A visibly peeved Ms Mahajan warned against such actions in the future.
"I am warning you... Dobara galti nahi honi chahiye (the mistake should not be repeated)," she told the member.
On July 24, Ms Mahajan had suspended six Congress members from attending the House for five days after they threw papers towards the Chair.
During those protests in the Well, it was alleged that Mr Thakur had shot the scenes using his mobile phone.
As the House met after adjournment at 1245 hours, Congress leader Mallikarjun Kharge wanted to know why action was not being taken against Mr Thakur whereas Mr Mann had faced suspension for two sessions for shooting video outside the House but in the Parliament complex.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)