Friends have revealed that Sir Edward Heath, the former Conservative prime minister, was sitting up in bed yesterday after treatment for a blood clot on his lung.

Iain Duncan Smith, the Tory leader, issued a statement wishing him a speedy recovery.

"I am sad to hear that Sir Edward Heath has been taken ill," he said.

"Naturally, we all wish him a very speedy recovery. The thoughts of the entire Conservative Party are with Sir Edward at this time."