Sexual harassment
Behaviour of this nature is sexual harassment which is defined under the Equality Act 2010 as unwanted conduct of a sexual nature that has the purpose or effect of violating an individual’s dignity or creating an intimidating, hostile, degrading, humiliating or offensive environment for them.
If you haven’t already done so and you feel able to do so without putting yourself at risk, you should tell your manager that you don’t like this behaviour and ask him to stop.
You can do this by email or ask a union rep or colleague to come with you to a meeting. Keep a record of this in case you need to raise a formal grievance or pursue a claim in an employment tribunal.
If the behaviour continues, you can pursue a grievance and/or bring a tribunal claim against both the individual manager and your employer.
If you have colleagues you can speak to about this, they may have overheard or experienced similar conduct. If this is the case, they may be able to provide both evidence and support for you.