The Subway Franchise aims to target 600 new stores in Britain and Ireland by 2015, creating about 6,000 new jobs.
There are currently 1,423 Subway stores in Britain, nearly a fivefold increase on the 2004 level, and 99 in Ireland.
"We find that no matter what country we're in, if we hit the right economic notes and appeal to the mass market, we're able to build the business very, very rapidly," Subway's president and founder Fred DeLuca told Reuters in an interview.
As well as traditional high street store development, the firm sees huge potential for non-traditional settings such as stations, convenience stores, hospitals, airports and petrol stations, mirroring a strategy being pursued by British baker Greggs, which currently trades from about 1,550 stores.
DeLuca said sales at British Subway stores open over a year were up 10 percent over the last 13 weeks.
Globally Subway has over 36,000 outlets in 98 countries from Afghanistan to Zambia. All stores are independently owned and operated by franchisees.
DeLuca dismissed the suggestion there was a danger the firm could reach overcapacity in Britain.
"Everybody eats three times a day; it's only a question of where they choose to eat. The longer-term trends are people eat out more often," he said.
"When we get to 2,000 stores, we'll have about one store for every 30,000 people (in the UK). That's actually quite low density for us. In the U.S. and Canada we have one store for every 12,000 people"
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