Former Chesterfield MP Tony Benn has been taken to hospital.
His spokesman said he was taken ill on Wednesday.
He is in a “comfortable” condition and his family have been visiting him, the spokesman added.
Mr Benn, 88, was Chesterfield’s Labour MP between 1984 and 2001.
A spokesman for the Benn family said: “Tony Benn was taken into hospital on Wednesday afternoon on the advice of his GP after feeling unwell. He is resting comfortably.”
He added that the Benn family had been “popping in and out” to see him.
In recent years Mr Benn has been president of the Stop the War campaign as well as a popular public speaker.
Mr Benn has topped several polls as the most popular politician in Britain.