Positive discrimination is unlawful in the UK but positive action isn’t.
What this means is that employers can choose to hire candidates from under-represented groups as long as they are as qualified for the role of other applicants.
You are not allowed to recruit a person purely on the basis of his or her age, disability, gender, race or religion, regardless of their ability to do the job. This would be committing discrimination under the Equality Act. It is also unlawful to set quotas to recruit or promote a specific number of people with a protected characteristic.
There are some exceptions, for example, it would be acceptable for a women’s refuge to require all members of staff to be women (to avoid causing distress to residents), or for a catholic school to require its headteacher and deputy head to be practising Catholics (to maintain the ethos of the school).
Organisations are allowed to take positive action, which could include encouraging people from particular ethnic backgrounds to apply for jobs, but the decision on who to select must be made on merit alone.
The rule of thumb from a legal perspective is that any positive action taken must be proportionate, or appropriate, to achieve what it is setting out to achieve without resulting in people without the relevant characteristic being treated less favourably.