If there is an arbitration clause you can go for arbitration. Other wise you can also file petition in nclt if he is a company. You have also the remedy of recovery suit in this case and you can attach his payments and receive the same

If you have supplied goods to particular projects. The under Indian Contract Act you request particular department to issue your payment. 

But as of now you can make complaint in consumer forum or Consumer court.

1) you can issue legal notice to contractor to pay your dues 

2) if contractor fails to pay file summary suit under order XXXVII of code of civil procedure to recover your dues with interest 

3) there is no privity  of contract with government hence you cannot get your dues directly from govt 

You can inform the concerned govt authorities of his default in making payments for supplies made to him by you showing all details  and agreed terms of payment and request to recover the due amount from his payment and remit to you. 

You can file summary suit for recovery the amount due from him. 

You can also make a police complaint if the circumstances gives a reasonable conclusion that he intentionally has left without making the payment to defraud you. 

File a money suit immediately. Last but not the least, I would suggest you to send the purchaser of your materials an Advocate Notice before rushing to the court. The contractor may be from anywhere in India. Once you have delivered the materials, the contract is fulfilled from one side and lack of payment by the contractor is violation of Contract Act. Make sure that the Advocate you recruit does not delay the suit. Normally Money Suit doesnt take long to be heard, hence make sure the Advocate you recruit fights for your cause. All the best in recovery of your money

You should send a legal notice and if he does not respond proceed as per the terms of the agreement. If there is no agreement then inform the government how he is evading his payments. You can file a suit for recovery or file a criminal complaint against him.

Regards 

You can give a legal notice to the said person, in case it is company issue a demand notice and if on notice he fails to pay the amount file a suit in case of individual or proprietorship or partnership firm and insolvency petition before the NCLT in case it is company. 

1.  Based on the available documentary evidence, file a private complaint of Cheating, Intimidation, Breach of Trust etc.... in the local Magistrates court, against the said Contractor.

2.  Once the Case has been admitted by the Magistrate, THEN issue Notice to the Govt. Dept.,  about the Contractors Criminal Case. AFTER this the contractor will clear all your bills.

Do you know the department? you can send a legal notice of demand to that department's head. 

You should hire an advocate and serve a legal notice for recovery of dues to the contractor through your advocate and also send copy of legal notice to the electricity department regarding recovery of dues from contractor.

If he fails to make payment you can initiate recovery suit against him.

You cannot write to to government to stop engaging his services for the reason that he has not paid you the amount after buying the goods from you.

You can issue a legal demand notice and then follow the procedure for recovery of money by due process of law which will be the proper and best option legally available before you.