Yes. It is unlawful to discriminate against a woman by subjecting her to a detriment where the discrimination arises out of and is closely connected with a relevant relationship such as an employment relationship. Provisions in the Equality Act 2010 which came into force on 1 October 2010 made it clear that post-employment discrimination is covered. An example of this would be refusal to provide a reference.
For further information concerning post employment discrimination in the context of references, see the relevant FAQs in our References FAQs.