Interior minister Amber Rudd apologized on Monday to thousands of British residents who arrived from the Caribbean decades ago and are now being denied basic rights after being incorrectly identified as illegal immigrants.

Prime Minister Theresa May is under growing pressure to resolve the issue of the so-called Windrush generation of migrants who arrived in Britain more than 50 years ago and have become victims of a recent tightening of the immigration system.

More than 140 lawmakers have signed a letter calling on May to resolve an anomaly that has meant many people who immigrated as children between 1948 and 1971 are being denied health services or prevented from working. Junior home office minister Caroline Nokes admitted on Monday that some people may have been deported in error, intensifying the row.