Dear Mr.Kumar,
First, there is difference between back wages and unpaid wages.
Back wages, literally and legally, means the wages for the period of of non-employment declared by the competent authority to be deemed as continuous period of service after adjudication of the issue of alleged illegal termination of employment by the employer.
On the contrary, unpaid wages means denied wages or wages not paid by the employer for whatever reason.
The claim for back wages can be presented before the Labor Court u/s 33-C(2) of the ID Act,1947 apart from filing a complaint to the area conciliation officer for prosecution of the employer against the offence of non-implementation of the award u/s 29 of the IDA,1947.
Claim for denied wages or illegal deductions can be filed u/s 15 of the PW Act,1936 before the designated authority under the Act. If it is only unpaid wages pertaining to any wage period, alternatively, a claim may be filed to the appropriate Government u/s 33-C(1) of the IDA,1947 and the Government, after inquiry, will issue orders to the concerned District Collector for recovery under the Land Revenue Recovery Act.
The defence of the employer in this regard can be only gainful employment of the workman elsewhere during the period of non-employment in case of an orders of termination set aside as illegal by the competent authority. Here, gainful employment does not mean self employment by the affected workman by doing some odd jobs to eke out a living during the period of his non-employment. Please take note that " competent authority " means here a Labor Court or any other appellate authority appointed under any establishment-specific law like the Shops&Estt Act to hear and dispose of the cases of termination in violation of the relevant provisions of discharge under the respective Act.
Another defence is " No work - No Pay " if the non-employment is ascribed to the voluntary absence of the workman or non-functioning of the entire establishment due to the operation of any law like the Disaster Management Act,2005.
I have not included the case of non-payment of wages by an employer in violation of the orders of any High Court u/s 17-B of the IDA,1947 for the simple reason that in such a situation, the appeal filed by the employer against the orders of reinstatement by the trial forum would be summarily dismissed by the Court on this ground alone.