No contract awarded to the lowest responsible bidder or to the highest responsible bidder, as the case may be, shall be assignable or sublet by the successful bidder without the written consent of the purchasing agent. In no event shall a contract or any part thereof be assigned or sublet to a bidder who had been declared not to be a responsible bidder in the consideration of bids submitted in response to advertisement for the particular contract.
65 ILCS 5/8-10-14