The action by employer and HR person shows zealous and vindictive mindset.
This is a prevalent practice and it is prevailing as employees do not pull the offenders to courts of law and neither employee unites and become member of trade unions.
Trade unions know precise ways to handle such individuals.
Although the companies prepare and keep personnel files on employees but do nto easily allow to examine these.
The labor laws demand to keep service cards and forms/formats to be kept and Inspectors appointed enactments e.g; Inspector under Shops and Commercial establishments Act, Labor Inspector etc can enter office and examine or even call record and registers in their office.
Therefore if employee has lodged complaint he may peruse even if by RTI route and obtain records from Labor Officials…………
Or demand to allow examining the personnel file and if matter lands up in court of law let employer bringing files and records in court.
Has the employer made some comments on conduct of the employee in relieving letter : Good or adverse? If good comments have been made then how come this employer and HR person is giving negative feedback?
In future always try and succeed to obtain good comments while in employment and also in relieving letter.
Be SMART and TACTFUL and obtain even if by email comments from next employer that past employer has given negative feedback and thus have some document in hand to agitate to past employer that it is with malafide intent to affect your employability and source of livelihood.
Thereafter you may issue a stern communication that during employment never and stinker or show cause notice has been issued to you on your conduct and rather your conduct and performance has always been appreciated then why negative feedback is being given after you have separated.
To the current employer you may reply that your conduct and performance has always been appreciated and conclude that since you have bought notice period from past employer to join current employer the past employer is acting in unfair manner.
Buying out notice period is not misconduct.
Your current employer which made you join immediately by buying out notice period must be aware of the practices in trade and it might also be acting in the same fashion with its employees that choose to separate.
Has the current employer compensated you for notice pay? If NO you have born this cost.
If NO you have made a mistake by not negotiating properly.
You have left past job and new job is in trouble.
You should have communicated even if by email that past employer is unwilling to agree to buy out notice period and has threatened that it shall render negative feedback.
If you are a member (or become a member) of trade union and let the President and Secretary take up the matter.
If you are not able to handle the matter on your own you may approach a competent and experienced labor consultant/service lawyer and proceed under expert advice of your lawyer.
It shall be wise to retain access to a lawyer always and keep on consulting on imp. matters.
The lawyer that has seen all of your docs can advice you the best.