"The Prime Minister will announce tomorrow that the UK's conventionally armed, nuclear-powered submarine fleet will be significantly expanded, with up to 12 new SSN-AUKUS boats to be built," Healey said in a statement released on the government's website on Sunday.
He said the new vessels will replace the seven Astute Class attack submarines currently in service.
In February, Starmer announced the UK's plans to raise defense spending to 2.5% of GDP from April 2027 and further to 3% of GDP in the next parliament.