The specifications upon which contracts are entered into by the Commonwealth for the construction, alteration, or repair of any public work shall, as far as possible, contain the minimum wage or wages which may be paid by the contractor or his subcontractors for the work performed by laborers and mechanics employed in such public work, and such laborers or mechanics shall be paid not less than such minimum wage or wages, and shall not be required to refund, directly or indirectly, any part of such wage or wages. The contractor shall certify that he is not receiving or requiring, or will not receive or require, directly or indirectly, from any employe any refund of any such minimum wage or wages.

Every contract entered into upon such specifications shall stipulate a penalty of an amount equal to twice the difference between the minimum wage contained in said specifications and the wage actually paid to each such laborer or mechanic for each day during which he has been employed at a wage less than that prescribed in said specifications. Every officer or person designated as inspector of the work to be performed under any such contract, or to aid in the enforcing of the fulfillment thereof, shall, upon observation or investigation, report to the department, board, or commission which made the contract award, all violations of minimum wage stipulations, together with the name of each laborer or mechanic who has been paid less than that prescribed by the specifications, and the day or days of such violation. All such penalties shall be withheld and deducted, for the use of the Commonwealth, from any moneys due the contractor, by the officer or person whose duty it shall be to authorize the payment of moneys due such contractor, whether the violation of the minimum wage stipulation of the specifications is by the contractor or by any of his subcontractors.