They can't. In the UK you are usually asked by the desk sergeant if you want a solicitor before they will question you.
Of course, you can be questioned while not being under arrest but again, you can ask for a lawyer before they question you.
I can't think a police officer could say in court: "He refused to be questioned before we arrested him" because you're not under any obligation to talk to the police in day-to-day life.
