He won three European Cups and five league titles with the Reds, whom he joined from Arsenal in 1974 having done the league and FA Cup double with the Gunners three years before.
A personal highlight was his pivotal away goal in the 1981 European Cup semi-final second leg against Bayern Munich.
Kennedy was diagnosed with Parkinson’s disease in 1984 and a testimonial game between Liverpool and Arsenal was held in 1991.
Later that year, he sold his medals and 17 England caps to help raise funds for his care.
A statement on Liverpool’s official website read: “The thoughts of everybody at Liverpool FC are with Ray’s family and friends at this sad and difficult time.”© PA Kennedy hits the cross-bar for Arsenal against Ipswich Town in 1973
Kennedy spent six years at Arsenal, winning the double in 1971.
The Gunners said on Twitter: “Everyone at Arsenal is greatly saddened to hear of the passing of Ray Kennedy.
“One of the giants of 71, Ray will be sorely missed by his friends, family and everybody at the club. Rest in peace, Ray.”
Liverpool’s Merseyside rivals Everton also offered their condolences, with the two teams set to play in the 239th derby on Wednesday night at Goodison Park.
The club said: “The thoughts of everyone at Everton Football Club are with the family and friends of Ray Kennedy following the very sad news of his passing.”© PA Scotland captain Bruce Rioch and Kennedy tussle for the ball during the 1977 Wembley clash
Former Liverpool striker John Aldridge paid tribute to Kennedy, tweeting: “Yet another magnificent Ex LFC star has passed away folks.
“Ray Kennedy what a player and lovely bloke who suffered so much with Parkinson’s disease for most of his life. He will definitely never walk alone. RIP Ray ynwa.”
Ex-Liverpool defender Phil Thompson tweeted: “More sad news with the passing of Ray, what a great player and such a wonderful team-mate RIP pal YNWA.”
Ronnie Whelan described his former team-mate as “an absolute legend at both Arsenal and Liverpool”, adding on Twitter: “Learned so much by watching him play. RIP Ray.”
Kennedy scored three goals for England, his first coming on his debut against Wales in March 1976.
A tweet from the national team’s account read: “We are deeply saddened to learn of the passing of Ray Kennedy at the age of 70. Ray won 17 caps for the #ThreeLions between 1976 and 1980, scoring three times.
“All of our thoughts go out to his family, friends and former clubs.”