1.When you have not signed the bond then, he don't have the right to say your work period is lesser than 2 years.
2. Ask him which law states that, employee can not work less than 2 years.
3. Better you may proceed legally, when you lost the job for foolish reason by previous employer.
If you have not signed any bond or any agreement. Also if your performance was good and that can be proved, then go ahead and send him a legal notice for defamation by illegal means through a lawyer.
Also once more call the first employer and ask him again the reason for the same, but this time record the conversation as proof.
Also you can speak with the HR team at the MNC and explain it why the negative feedback was given. Also tell them that you can give reference of your direct manager or colleagues who can prove that the first employer is speaking rubbish.
Try to satisfy to who, who has given new Job, if not satisfied, then you should join your previous job and start regular your working, I think you don't have to go in dispute matter,it will waste of time and money.