Hello Sudhabindu Dhar, it is to inform you that we have to follow some basic rules while working in one or another organization. In general, for every government recruitment there are some rules & regulations to be following before offering job to an Individual.
Case 1:- New Employer asks for NOC
1) In this case, the new employer asks for producing "No Objection Certificate" at the time of Interview or final round of the recruitment whichever is applicable.
2) Hence in order to produce NOC at the time of your new recruitment, I suggest you to intimate in your office "Before applying for job" in the below mentioned format.
The ...(old employer)
Sub: Intimation of applying for "......" recruitment
With due respect, it is inform your goodself that I am applying for ....recruitment and request to issue "No Objection Certificate" at the time of final Interview..and mention your concern.
Thanking You Sir
3) So as you are already informing your old organization before applying for recruitment, they have to provide you NOC once you get selected finally.
Case 2:- New Employers asks you to apply through proper channel (Means from your old organization)
1) On the other case, you can request your old employer to forward your recruitment application through proper channel (with the letter head of your office) to the new employer.
2) Then once it is sent through proper channel, your application will be considered for attending the recruitment.
>> So you have two cases to be followed according to my knowledge and the CASE 1 would be the better one for you and this can be followed by employees generally. Hope my suggestions would be helpful to you.