He said: “Now we must not let a positive result bring a negative mindset but I must say I could use your help in this department.
“We are asking for prayers, good energy, love and support to be sent our way.”
He said his daughter had brought “cases of photographs to reflect upon and keep us strong through our recovery”.
He added: “My biggest ‘ask’ is for my darling wife, Patricia (Popea).
“She has been through so much and does whatever it takes. She is an unbelievable woman of strength.
“Please also keep our wonderful caregivers in your prayers.”
The singer, who was born in India and grew up in Leicester, topped the UK singles chart with his hits Release Me and The Last Waltz in the 1960s.
He also represented the UK at the Eurovision Song Contest in 2012 with the song Love Will Set You Free, finishing second last.