The Leader of the Labour Party, Ed Miliband, has paid tribute to Dr Joe Hendry.
"I am deeply saddened by the death of Joe Hendry. I met Joe on several occasions and his passion and commitment to Carlisle and Cumbria always shone through.
"I know he was incredibly proud of the city he called his home and ambitious for its future.
"His love of the Labour Party was equally strong. He led Labour out of opposition after 13 years and since becoming Leader of the Council has worked hard to keep the promises he made to local people.
"His loss will be felt across the whole community. My thoughts are with Monica and his two sons at this sad time."
More top news
Decommissioning the nuclear site at Sellafield faces continued delays and an overspend of £913 million, according to an official report.
New law will protect the dignity of both men and women, the Government says.
Transport Secretary Chris Grayling has survived a vote of no confidence, amid claims his credibility will "never recover" .