The marathon was originally planned to go ahead on April 5, but was rescheduled to September in the hope that guidance would allow it to go ahead in 2020.
Sublime Racing has been working over the past few months with stakeholders, Peterborough City Council and Nene Park to be ready should restrictions be lifted in time to run the event as planned.
To run the event, the organisers would need to see the government remove the restrictions on events with more than 1,000 people and there would need to be confidence that staff, volunteers, runners and local residents would be safe.
Race director Martin Jennings explained the decision in a post on social media, stating: "With no clear understanding of when the government will be able to lift this ban, it is impossible for our stakeholders to officially commit to the event and as such we are all progressing on a “What if” basis.
"We continually assess the implications this uncertainty has on our runners preparing for the event. We feel that two-months is the minimum period for which we should offer absolute assurance that the event will go ahead, and we are simply not able to do that.
"We are also extremely sensitive to the feelings and considerations of the residents who we affectionately refer to as our Race Neighbours. The restrictions around Covid-19 are starting to relax, however we are very aware that some of our Race Neighbours have been affected in the most devastating way by this crisis and we have to consider if September may be a little too soon for them even if the ban is lifted.
"We are also very conscious of ensuring the safety of our Team, Race Makers, and of course our runners, and whilst we have many plans to significantly reduce the risk of transmission, there is no doubt that delaying the race further will reduce that challenge.
"We are also incredibly passionate about the standard of event that we host. If you have taken part in a Sublime event before you will know the level of detail that goes into every aspect of the day. We are concerned that this will be heavily compromised by many of the mitigations that would need to be implemented, such as the lack of baggage, catering and beautiful venue setting.
"With all the above in mind, we have made the very difficult but hopefully understandable decision to defer the event until April 11, 2021.
"As Race Director of the Enervit Peterborough Marathon, I would like to personally apologize to Enervit, all of our runners and to the very special Sublime team, from the Directors to the Race Makers who are all volunteers, for the difficult challenges we have faced this year and to thank you again for your incredible support and understanding."
Participants will be transferred to the new date and send a notification once this has been processed. Those unable to attend the new date of April 11 should email email@example.com to find an alternative.