Can HMRC see offshore bank accounts?

I'm a UK taxpayer, and I have some offshore bank accounts. I'm just curious, can HMRC see my offshore bank accounts? I understand that HMRC has the authority to investigate my tax affairs, but does that extend to my offshore accounts? Are they able to access information about these accounts, or do I have something to worry about? I'm just trying to be proactive and make sure I'm complying with all tax regulations. Can you provide some clarity on this matter?