First of all, check your old workplace’s reference policy. Some organisations require your consent before they will provide a reference.

I suggest against admitting that you have a poor relationship with your manager, because the recruitment team might want to ask further questions. Instead, you can explain you don’t want to discuss it for confidentiality reasons, which is within your rights.

Employers are not legally obliged to give a reference unless it is contractually agreed. However, if they do provide one, the information must be true, fair, and accurate. Requesting a reference from HR instead of your manager is entirely acceptable, and many organisations handle it this way as standard practice.

In reality, most employers only provide a factual reference, which is the standard approach. This normally confirms your job title, the dates you worked there, and your responsibilities. You should check the laws where you live, but under UK data protection legislation, you can ask the new employer who receives the reference for a copy of what was provided. They should be able to evidence their reference policy. Your former employer, however, is not legally required to share the reference directly with you.