Lewis Hamilton leads tributes to Michael Schumacher on F1 great's 50th birthday

Lewis Hamilton (R) has described seven-time world champion Michael Schumacher as a "true inspiration". Clive Mason/Getty Images

Five-time Formula One world champion Lewis Hamilton has led tributes to Michael Schumacher on the Ferrari great's 50th birthday.

Schumacher has not been seen in public since he suffered severe head injuries in a skiing accident five years ago and is being cared for at his home in Switzerland.

Hamilton's tally of five championships and 73 Grand Prix wins is second only to Schumacher, who holds a record seven world titles and 91 wins.

"Wishing you a happy birthday, Michael," Hamilton posted on Instagram.

"50 years of life and a legacy that will last forever. What an honour it is to say that I have raced with you.

"You've always been a true inspiration to me and the entire world.

"Keep fighting, Champ."

Schumacher's family released an update on his condition on Wednesday, in what was a rare message posted to the public.

"You can be sure that he is in the very best of hands and that we are doing everything humanly possible to help him," the family said in a statement on Schumacher's official Facebook page.

"Please understand if we are following Michael's wishes and keeping such a sensitive subject as health, as it has always been, in private," it added.

Former world champion Nico Rosberg, who was Schumacher's teammate at Mercedes from 2009 to 2012, also paid tribute to his German compatriot.

"Happy 50th, Michael! Stay strong," Rosberg posted.

"Wishing you and your family and every Schumi fan out there all the best! #keepfighting."