Frank Judd, who was an MP for Portsmouth between 1966 and 1979, has died age 86.
Lord Judd also served as minister for the Royal Navy, a former director of Oxfam, and became a life peer in 1991.
Following his death, tributes from fellow party members and friends have flooded in.
The current Labour MP for Portsmouth South, Stephen Morgan was endorsed in his 2017 election campaign by Lord Judd, and the two met on a number of occasions.
He said: ‘Incredibly sad to share news of the death of Lord Frank Judd of Portsea, former Labour MP for Portsmouth.
‘As a tireless champion for human rights, and dedicated constituency MP, he was both inspirational and a great friend.
‘Portsmouth has lost a true hero. RIP Frank.’
Amanda Martin, former president of the National Education Union, added: ‘The Labour Party lost a wonderful man today – love and condolences to his family.’
Leader of Portsmouth City Council, Cllr Gerald Vernon-Jackson, a Liberal Democrat, was also fulsome in his praise of Lord Judd.
He said: 'I met with Lord Judd on many occasions - he was a really nice guy and a true servant to the city of Portsmouth.
'It was really good to have somebody of such long-standing experience still fighting for the city, even as recently as a few years ago.
'My sincere condolences go to his family and friends.'
Lord Judd served as Portsmouth West MP between 1966-1974 when the seat was abolished. He won Portsmouth North MP that year, serving in the seat until 1979.
In 1975, while also serving as navy minister under prime minister Harold Wilson, he visited the Portsmouth Detachment 43 Command Workshop REME, at Hilsea Lines, to meet the men working at the establishment and for a briefing on the work done there.
Three years later, he joined protesters in the city and called upon the government to tighten safety regulations for tower blocks, after a toddler fell to his death at the Portsdown Park estate.
During his time as an MP, Lord Judd was critical of the redevelopment plans for the city as it looked to modernise in the post-war era.
Speaking in 1973, Mr Judd claimed a ‘lack of strong leadership’ meant much of the city was a ‘disgrace’, citing extensive damage to buildings following the war and questioning the quality of new constructions.
In 1984, Lord Judd was critical of the council’s plans to build a sports complex on the city’s old Hilsea airport site.
The leader of the Conservative Party in Portsmouth, Cllr Donna Jones, has also offered her condolences to Lord Judd’s family.
She said: ‘I am very sad to hear of the passing of Lord Judd. A former MP and a member of the House of Lords, he served the city for many years.
‘He spent his latter years down in Old Portsmouth and was a well-recognised figure – our thoughts are with his friends and family at this sad time.’
Labour Party leader, Sir Keir Starmer, said: ‘RIP Frank Judd. A great Labour internationalist who fought for peace, human rights and social justice.
‘He will be missed by us all.’
Baroness Angela Smith, Labour leader in the House of Lords, added that Lord Judd was always supportive of his colleagues.
She said: ‘As he got older and needed two walking sticks, he would use one to wave a greeting to friends, shouting out that he had enjoyed their speech or an interview he had seen.
‘His Labour Lords’ colleagues both admired and had enormous affection for Frank, and we valued his friendship.’
Lord Judd leaves behind his wife, Christine, and their two daughters.