The UK had been set to host two Diamond League meetings in the capital in July and another in Gateshead in August.
But the latter has been scrapped altogether, while London’s traditional two-day Anniversary Games has been cut back.
In addition, it will move from its weekend slot to Tuesday, July 13 in order to avoid clashing with an already packed sporting calendar.
The event will take place after both the Euro 2020 final and the final day of Wimbledon, as well as avoiding a clash with the British Grand Prix the following weekend.
London’s Diamond League event takes place just 10 days before the revised Olympics get under way in Tokyo, and organisers will hope leading British and international athletes will use it as a final preparation event for those Games.
London is one of 14 events on the calendar, which begins in Rabat, Morocco on May 23 and reaches its season finale in Zurich from September 8-9, the only two-day meeting on the 2021 calendar.