Complain to Bar counsel. Disciplinary action will initiate agasint him. 

you are at liberty to change your counsel if  you so desire 

2) request him to return case papers give his NOC and engage another lawyer 

Yes if he has acted in  conflict of interest it is process misconduct.  You can complaint to respective bar council for the same

See this is misconduct by lawyer you should complain before bar council and change your lawyer.

If you wish, you can change the lawyer

1. Ethically he should not appear for your opponent when he is already appearing for you against the said person/party.

2. Change the lawyer in your own interest.

3. For changing Advocate, you won't have to show any reason.

Dear Client 

you can complain against the advocate in Bar council for his professional Misconduct by appearing for opposite party in which you are the other party.

but if you are not party in those cases then you cannot complaint against him. 

A lawyer who has signed a Vakalatnama and is your counsel cannot argue against you. This is illegal. File a complaint against him in the state bar council.

Regards 

Is the opponent a govt department? Furnish complete facts.

if you're not satisfied with your advocate, engage another advocate to take up your case. 

you can take NOC and engage other expert. 

You can change the lawyer for the same reason that  he is simultaneously appearing for both the parties.

If he refuses then you can even lodge a complaint against him for this before the bar council of India

1. As per the information mentioned in the present query, makes it clear that this is the professional misconduct by the lawyer.
2. He should not have done this as this is against the principle of fair justice.
3. He can do that but that is also only after discharging himself from your case, but surely should not come against you on his behalf in the present case.
4. You should file a complaint against him in the BCI.