The Shirayama Corporation, which bought the former Greater London Council headquarters, said the decision represented its apology to the British people - and all other people in the world - who suffered from Japanese cruelty during the Second World War.
The corporation said it hoped its move would persuade the Japanese government to make a formal apology to all who suffered and pay proper compensation to them.
Shirayama initially refused to allow the ceremony but then agreed to it only if British veterans paid for seven Japanese veterans to attend - an idea rejected as financially impossible.
Bert Reeves, 74, chairman of the County Hall branch of the Royal British Legion, welcomed the move, which will allow veterans to hold a service and lay a wreath at the war memorial.
"It is a complete about-turn and we plan to commemorate VJ-Day accordingly," said Mr Reeves. "The branch felt it was important to be there on the 50th anniversary ... rather than leave the memorial unnoticed."Reuse content