Thomas, 38, retired from football a year ago and started a men’s designer clothes business after finishing his career at Crewe.

In a message to Palace fans yesterday he said: “Thank you all for your wonderful messages of support. They mean a great deal to me.

“I have been diagnosed with chronic myeloid leukaemia and have been receiving treatment over the last three weeks, which has improved my blood count. All of this has been a huge shock to me and my family. That is why your support is so special.”

PFA boss Gordon Taylor said the players’ union had been informed.

He said: “Geoff has been in touch with us and we shall do whatever we can to help him.

“It is shocking news but we always take care of our members — even when they have retired.”

A Crewe spokesman said: “We were not aware of this until today and were very sad when we were informed about Geoff’s illness.

“He had two spells at our club and was always a very popular figure about the place.”

Thomas made his name at Rochdale and Crewe, before becoming a big favourite with Palace.

He won nine England caps, was never on the losing side and captained Palace in the 1990 FA Cup final against Manchester United.

The news about his illness comes 24 hours after Millwall fans revealed they are raising funds for Keith Weller.