He has cited personal reasons behind this move.
Kumar's resignation comes close on the heels of the resignation of Mukul Rohatgi from the post of the Attorney General of India on June 18.
The channel reported that the Additional Solicitor-General Tushar Mehta is now the front-runner for the post as he has already been leading the arguments in many cases with great political implications.
Ranjit Kumar had lobbied the Gujarat government in the Sohrabuddin Sheikh Encounter case.
"I have resigned due to personal, family issues which I need to attend to and was not able to due to my work", Ranjit Kumar is learned to have written to his colleagues. Ranjit Kumar's resignation letter found today in the office of Law and Justice Ravi Shankar Prasad. Another reason which could be behind the resignation is that the Modi government wants a new legal team which has more teeth and is more discreet.
In June, the term of Kumar was extended by the government.
The senior advocate was appointed solicitor general in 2014, soon after the BJP-led NDA government came to power.
K.K. Venugopal took over as Attorney General after Rohatgi stepped down.
There was speculation a few months ago that the Supreme Court collegium was considering Kumar's name as a judge of the apex court. Mr Rohatgi has resigned over declining on his service extension in June this year.