Pontins used an “undesirable guests” list which blocked potential customers from booking.

Now, the owner of Pontins has entered into a legal agreement with the human rights watchdog after a whistleblower revealed it was using an “undesirable guests” list to exclude Gypsies and Travellers.

Britannia Jinky Jersey Limited is working with the Equality and Human Rights Commission (EHRC) to prevent racial discrimination after a Pontins employee said the holiday park company was operating a discriminatory bookings policy.

It said staff monitored calls and refused or cancelled bookings made by people with an Irish accent or surname, and Pontins’ commercial vehicle policy excluded Gypsies and Travellers from its holiday parks.

The EHRC said that by carrying out these practices, Pontins was "directly discriminating on the basis of race" and breached the 2010 Equality Act.

Britannia Jinky Jersey Limited said it was working to enhance its staff training and procedures to further promote equality throughout the business.

Alastair Pringle, EHRC executive director, said: "It is hard not to draw comparisons with an undesirable guests list and the signs displayed in hotel windows 50 years ago, explicitly barring Irish people and black people.

"Banning people from services based on their race is discrimination and is unlawful. To say that such policies are outdated is an understatement.

"It is right to challenge such practices and any business that believes this is acceptable should think again before they find themselves facing legal action.

"We will continue to work with Pontins and Britannia Jinky Jersey to ensure that our agreement is adhered to and its practices improve."

Downing Street condemned the blacklist as “completely unacceptable”, with the Prime Minister’s official spokesman saying: “No-one in the UK should be discriminated against because of their race or ethnicity.

“It’s right that the Equality and Human Rights Commission and Pontins investigate and address this.”

A spokesperson from Britannia Jinky Jersey said: "Britannia Jinky Jersey Limited has agreed to work together with the Equality and Human Rights Commission to further enhance its staff training and procedures in order to further promote equality throughout its business."

Pontins must now investigate the “undesirable guests” list as part of the agreement before taking appropriate action and ensure lessons are learned.

It must commission a review into its booking and commercial vehicle policy and consider any recommendations, and provide equality and diversity training for staff each year.

If it does not adhere to these terms, the EHRC can launch a full investigation.