No, this is not legal. Quoting from the Table Tennis England Rules of the game:
Strike – 2.5.7 – A player strikes the ball if he touches it in play with his racket, held in the hand, or with his racket hand below the wrist.
(my emphasis) and
Procedure – 2.7.1 – The ball, having been served or returned, shall be struck so that it touches the opponent’s court, either directly or after touching the net assembly.
i.e. the ball must be struck in order for it to be a legal return, and a strike can happen only if the racket is held in the hand. This then results in the loss of the point:
Conditions – 2.10.1 – Unless the rally is a let, a player shall score a point
Incorrect return – 22.214.171.124 – if his opponent fails to make a correct return;