A group of 75 MPs has joined animal welfare activists in calling for the release of 15 penguins “trapped in a basement without sunlight or fresh air” at the Sea Life London Aquarium.

The captivity of 15 gentoo penguins at the riverside attraction, a short walk from Parliament, is “un-British”, the MP leading the campaign said.

Members of Parliament from across the political spectrum signed the open letter calling for an urgent review into the welfare of the birds.

The aquarium, owned by Merlin Entertainments, opened its first penguin exhibit in May 2011, introducing 10 gentoo penguins from Edinburgh Zoo, which “have now endured 14 years in a basement” equipped with a pool of only six to seven feet deep, according to campaigners.

In a letter to Environment, Food and Rural Affairs Secretary Emma Reynolds, the group asked her to “consider whether the penguins should be relocated to a more suitable facility better aligned with their behavioural, ecological and physiological needs”.