52. Where a claim includes a complaint under section 6(4A) of the Sex Discrimination Act 1986(1) relating to a term of a collective agreement, the following persons, whether or not identified in the claim, shall be regarded as the persons against whom a remedy is claimed and shall be treated as respondents for the purposes of these rules, that is to say —
(a)the claimant’s employer (or prospective employer); and
(b)every organisation of employers and organisation of workers, and every association of or representative of such organisations, which, if the terms were to be varied voluntarily, would be likely, in the opinion of a chairman, to negotiate the variation;
provided that such an organisation or association shall not be treated as a respondent if the chairman, having made such enquiries of the claimant and such other enquiries as he thinks fit, is of the opinion that it is not reasonably practicable to identify the organisation or association.