The singer has confirmed that a chest infection has led him to axe his appearance at the free BT London Live event on Saturday (July 28).
Jones has also pulled out of a gig at the Isle of Wight's Osborne House, which had been scheduled for Sunday (July 29)
Full refunds for the Osborne House concert are available at the point of purchase.
Jones is next scheduled to perform on Friday, August 10 in Newmarket, Suffolk.
Earlier this week, Jones insisted that he will sign on for another season of The Voice UK only if he is told who the other judges will be.
Watch Sir Tom Jones perform 'I Bet You Look Good on the Dancefloor' below: