A person shall be disqualified if, and for so long as, there subsists a contract entered into by him in the course of his trade or business with the appropriate Government for the supply of goods to, or for the execution of any works undertaken by, that Government. Explanation.—For the purposes of this section, where a contract has been fully performed by the person by whom it has been entered into with the appropriate Government, the contract shall be deemed not to subsist by reason only of the fact that the Government has not performed its part of the contract either wholly or in part.