Runner Steve Burrows, 49, of Plymouth, Devon, said he was disappointed by the mix-up and urged organisers to amend all finishing times.
“My watch recorded quite a bit over when I finished, but I didn’t pay too much attention because that’s the last thing you’re looking at when you finish a marathon,” he said.
“It was only a day or two after when quite a lot of people commented that it tracked with so many people.
“Yes they’ve apologised, but what most people want now is their times correcting to reflect what they should have.
“These races aren’t cheap. We pay a lot of money to do that. It’s all very well getting your medal and t-shirt but most people aren’t overly fussed with that, they want the official time.”
It is not the first time a race in Newport has been measured incorrectly. In 2015, the Newport Half-Marathon was later found to have been 636m short.
