Please understand, one you have signed your non-disclosure agreement you need to abide by it. Since the company hiring you seeks your salary details and relieving letter from the present company.
In case of verification, the present company gives a negative report about you, the possibility of losing the new job. Therefore, you please convince your news employer, else you need to agree to pay your month's salary to the present company. Option is yours.
18th March 2015 From India, Bangalore