There are nine protected characteristics under the Equality Act 2010. It is unlawful to discriminate against a person on the grounds of these characteristics.
• age
• race
• sex
• sexual orientation
• religion or belief
• disability
• gender reassignment
• marriage and civil partnership
• pregnancy and maternity
See this: fairplayforwomen.com/equality-act-2010_womens-rights/
EHRC statutory code says:
2.55 Sex is a protected characteristic and refers to a male or a female of any age. In relation to a group of people it refers to either men and/or boys, or women and/or girls.
2.56 A comparator for the purposes of showing sex discrimination will be a person of the opposite sex. Sex does not include gender reassignment or sexual orientation.
“Sex is clearly described here using the commonly accepted words man and women. A woman must not be discriminated against compared to a man based on her biological sex. If a transgender person does not possess a gender recognition certificate then their legal sex is still the same as their biological or birth sex”
There are six main areas set out in the Equality Act 2010 that acknowledge the need for women-only spaces, services, roles and activities and makes it lawful to exclude males (including trans-identifying males). In all cases the use of an exemption must be a proportionate means to achieve a legitimate aim. There are no blanket rules since each situation must be considered on its own merits and due regard must be given to all groups affected by invoking the exemption. The least discriminatory option must always be chosen.
It goes on to describe single sex accommodation, sports, women only shortlists, women specific services etc.
eg
Considerations of privacy or decency might require a public changing room or lavatory attendant to be of the same sex as those using the facilities.
Unemployed Muslim women might not take advantage of the services of an outreach worker to help them find employment if they were provided by a man.
A counsellor working with victims of rape might have to be a woman and not a transsexual person, even if she has a Gender Recognition Certificate, in order to avoid causing them further distress.
Anywa, have a look at the link, it's all there.