The Mini Coupe and Roadster will be built at BMW's plant in Oxfordshire, creating up to 1000 jobs.
The cars, which will be unveiled at the Frankfurt motor show on 15 September, are expected to go into production within the next three years.
Speaking about the news, business secretary Lord Mandelson said: "The production of two new Minis is very good news for Oxford, and for the UK car industry.
"It is a demonstration of BMW's long-term commitment to the UK.
"British drivers have had a long love affair with the Mini and I'm sure that this will continue for many years to come."
It marks good news for Mini, which earlier this year shut its site for a week and cut 850 jobs.
Production was also suspended in June due to a strike in France involving a firm that supplies bearings for the cars' steering units.