"There are many of us who will miss him. Lars Werner was deeply rooted in the labour movement. He had a warm heart and strong sense of class. A large and loved political figure has left us."
Werner lead the Left Party for nearly two decades, between 1975 and 1993.
Sjöstedt's predecessor, Lars Ohly, tweeted on Saturday afternoon: "The Left Party is in mourning. Lars Werner is dead. And I have lost a support and a friend."
CH Hermansson, Left Party leader between 1964 and 1975, also reacted to Werner's death.
"I will miss Lars Werner terribly and am devastated after hearing the news. We worked together for many years to renew the party as a modern left movement. He was always very loyal and reliable," said Hermansson.
Werner, born in 1935, was trained as a mason and became chairman of the masons' union in 1972.
He was also a member of parliament between 1965 and 1994.
In the 1960s, Werner campaigned for the party, then known as the Swedish Communist Party, to become more independent of its Soviet counterpart.
It was under Werner's chairmanship in 1990 that the party changed names from the Communist Left Party (Vänsterpartiet kommunisterna) to the Left Party.
When Werner left the leadership post three years later, he was replaced by Gudrun Schyman.
Werner died around 5pm on Friday January 11th.
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