Pret a Manger is considering a stock market flotation within the next 18 months that could value the sandwich chain at between £150m and £280m.

Founder Julian Metcalfe told City A.M. he wants to float the business and is in preliminary talks with bankers.

Mr Metcalfe, who with co-founder Sinclair Beecham owns two-thirds of the company, said an IPO would help fund the group's international expansion plans.

Pret's other major shareholder is the fast food giant McDonald's, which paid £50m for a 33% stake in the company in 2001.

Pret opened its first store in London in 1986 and has branches across Britain and in New York, Hong Kong and Singapore. It posted pre-tax profits of £8m last year from revenues of £190m.