If you are at risk of persecution in your country and are unable to return because of this risk, you may be recognized as a refugee and be given permission to remain in the UK. If this applies to you, you should claim asylum.
Your right to protection is based on the 1951 Refugee Convention which is also part of UK law. The UK authorities must protect you from ‘refoulement’: your forcible return to a country where you are at risk of persecution.
If you do not qualify as a refugee, but there is a real risk that you would be killed or suffer serious harm if you had to go back to your country, you may be granted humanitarian protection.