Hundreds of people are expected to rally in Portsmouth on Saturday in protest at job cuts imposed by defence company BAE Systems.
The company announced last month that more than 900 jobs are being axed.
More than 10,000 people have signed a petition calling for shipbuilding to remain in Portsmouth.
"It's not just about the jobs... it's going to affect the industries in the pubs, restaurants, schools and even transport," Lisa Fletcher, a community support officer for Unite told Sky News.
BAE systems and the Government claim warship building in the UK needs to be consolidated into one site on the Clyde in Scotland if it is to stay economically sustainable.
The end of shipbuilding is a huge blow to the city, which has a long maritime tradition. Ships have been built in Pompey for more than 500 years.
Unite national officer Ian Waddell told the Daily Echo: ''Portsmouth has a proud 500-year history of shipbuilding. It is a waste and a tragedy that the Government is allowing this legacy to end.
''BAE Systems' workers, their families and the local community are calling on the Government to think again and secure shipbuilding in Portsmouth for another 500 years.
''As the ultimate owner of the Portsmouth dockyards, the Government can generate opportunities to save these valuable shipbuilding jobs and skills.''
However, trade union leaders are hoping the Government will consider a stay of execution, and opt for a three-dock solution that would also mean fewer job losses at the shipyards in Scotland which have also been affected.
"We believe that there is a solution, whilst that would mean job reductions right across the three yards, we believe we would be able to retain the capability," says Prospect union's negotiator John Ferrett.
The redundancies will begin as work on two aircraft carriers comes to an end.
Gary Cook, GMB union's regional officer, said: ''Not only is the coalition government prepared to throw more than 1,000 highly skilled shipbuilders on the scrap heap, many of whom will be destined for a life on benefits, but they are also playing fast and loose with the national security of these British Isles by having no plan B for warship building."