Yes you need to pay tax on it, as the property is in the UK and generates the income. Your income is tax free if its earned outside of the UK. In the UK, it is taxed.
The only way to avoid any tax obligation would be to transfer ownership of the property to a company structure. But if you have a mortgage, this is unlikely to be acceptable by the bank, so isn’t an option.
The other way would be to minimise your tax obligation - by recording rent income, against mortgage interest, property upkeep, fees, bills, etc etc. Whatever is left is your profit - but you have a personal tax allowance of around £11K, so you would only need to pay tax on the portion of profit above that amount. You’d do this via Self Assessment with HMRC. I think the rules around what can be claimed for rental properties changed fro the 16/17 tax year, so you’d want to read in to that more (or keep all your receipts and then speak to an accountant).