As you are claiming, it will affect your policy. Yes, you need to declare it on future applications. If Tesco advised on a recorded phone call, or by email , that it would not affect your no claims, raise a complaint. Your complaint is that you would not have claimed had you been told your No Claims Bonus would be affected. As your insurer, the information they offer is regulated advice and, as such, they have breached the Financial Service and Markets Act 2000 if they have provided incorrect advice that leads to financial detriment (loss of no claims and increased premiums). Contact the financial ombudsman service as well. It is wrong for them to change their stance unless it was an innocent error.