Mike Clancy, Prospect general secretary, said:
"It is welcome that this announcement has finally been made following damaging delays from government that caused huge uncertainty for the industry. This was a critical decision to securing the future of the Rosyth yard where we are a leading union.
“Events in the Gulf this summer have shown that 19 frigates should be an absolute minimum for the Navy. So this first order of five warships must be followed up by further orders. This will maintain the drumbeat of production and make sure further capability gaps do not occur.
"This government has a lamentable record on shipbuilding, with yards closing and skills lost. These workers need more than warm words and a new tsar, they need concrete action.
"These frigates were always going to be built in the UK, but workers need a cast iron guarantee from the prime minister that new naval support ships will also be built in our yards and UK workers will not be left high and dry while vital work and taxpayers’ money is sent abroad."