The wealthy star of the Dragons' Den series is in a Darlington hospital after falling ill at the headquarters of his gym company in the County Durham town.
A spokeswoman for the Bannatyne Group said: "Everyone at the company is very concerned and upset, but we know that Duncan is a very strong person and we are confident he will make a full recovery - everyone wishes him well."
Bannatyne, 63, who lives near Middlesbrough, was born in Clydebank.
His business interests now include health clubs, hotels, property, media and transport and he is best known as a tough-talking businessman on the TV show.
Last night his daughter Abi said he was in a stable condition.