Opting customers in to email marketing without consent

Working for a company based in England.

The company has a customer loyalty system which requires customer data. We sign the customer up to the loyalty program in person which involves asking the customer for their email.

When signing the customer up to the loyalty program there is an option to tick a box which opts the customer in to receive marketing emails. Higher ups have explicitly advised that we do not need to ask the customer if they want to opt in. We are expected to tick this box regardless.

Furthermore, when a customer returns to the store and makes a purchase, we are being told to check on the system if the customer is opted in to marketing. If they are not, we are expected to opt the customer in without asking. This means that if a customer has unsubscribed from marketing we are potentially resubscribing them without consent.

This is a tracked metric which we are being pushed to increase and employees are being ranked against eachother.

Each employee has signed a document to state that they understand the data protection act. I am questioning my liability if I were to proceed as the company expects especially given the pressure I am under to meet this metric or face disciplinary measures.