Section 43(v) in The Bihar Industrial Disputes Rules, 1961
(v)Where there is one trade union in an industrial establishment, registered under the Indian Trade Union Act, 1926, and such trade union does not represent fifty-one per cent or more of workmen, the representatives of workmen on the Works Committee shall be nominated by the trade union in proportion to its respective strength and the remaining number of representatives of the workmen on the Works Committee shall be elected by workmen themselves.
