Tax deducted from salary bye the employer but not paid to go

We are working in a limited company. Our employer deducted tax at source from our salary but not paid to the appropriate authority since from July.14 and also not provide me the Form-16 (For all the employees). They issued all the employer a letter mentioning the Form-16 figure, accordingly we filled the I.T. return for the F.Y. 2014-15 & 2015-16 (F.Y.2016-17 yet to fill). As no TDS reflected in Form 26AS I.T. department send us the demand notice for those F.Y. So what to do in this situation, please help us.

Regards

SANTANU