1. Notice period is not just dependant on T&C inserted in any private contract that employer has signed with employee e.g. contract of employment, appointment letter!
The employee should tender some reasonable notice, affirm that no tasks are pending at his/her end and offer to handover the charge in writing under proper acknowledgment and thus build favorable record in writing.
You may go thru many threads that you may find relevant and download the judgments too:
https://www.lawyersclubindia.com/forum/Dispute-on-resignation-acceptance-106751.asp#.U-Hax-OSwb8
https://www.lawyersclubindia.com/forum/Whether-notice-period-has-to-be-given-during-probation-91808.asp#.UwDFP0eBmXU
https://www.lawyersclubindia.com/forum/Notice-period-nad-absconding-employee-92345.asp#.UpMpStIW1MA
https://www.lawyersclubindia.com/forum/Mnc-issuance-of-experience-certificate-re-leaving-letter-92229.asp#.UoiogdKAqWM
https://www.lawyersclubindia.com/forum/One-sided-notice-period-92171.asp#.UoiondKAqWM
https://www.lawyersclubindia.com/forum/Query-regarding-relieving-letter-and-continuity-bonus-92151.asp#.Uoio6NKAqWM
https://www.lawyersclubindia.com/forum/Whether-notice-period-has-to-be-given-during-probation-91808.asp#.UoSg3nCAqWM
https://www.lawyersclubindia.com/forum/Notice-period-92146.asp#.UoTD33CAqWM
https://www.lawyersclubindia.com/experts/Different-notice-period-for-employee-and-employer-during-probation-432151.asp#.UoTGvHCAqWM
2.Has the resignation been accepted in writing or do you have any evidence (audio/visual)?
Has the notice period been mentioned in notice of resignation/resignation?
Even if NO, narrate in writing under proper acknowledgment that on dated…………………Mr/Ms…………..accepted the resignation and must have forwarded it to good offices of appointing authority, MD etc and no tasks are pending at your end and to whom you should handover the charge under acknowledgment on the spot!
Resignation should be addressed to good offices in writing preferably by letter thru redg. post.
2. Disruption to perform the duties be informed to good offices at once.
3. You may affirm that notice pay in lieu of CORRECT notice period be adjusted in FnF statement and it be supplied to your verification and acceptance.
4. You can mention the joining time offered to incoming employees and notice period/exit time for outgoing employees and that it is heavily inclined towards employer and detrimental to the interest of employee.
5. You are once again erring by accepting the less joining time from next employer than notice period and should have stated existing notice period in employment application hence joining time required by you
6. Ask the next employer to buy your notice period without any conditions and pay it on the day you join, and that you be absorbed without acceptance of resignation/relieving letter as current employer is unwilling to issue it and it is due to less joining time granted by future employer.
7. Defend your interest in the best possible manner.