Routes across the country are measured using a bicycle fitted with a counter to record the distance.

But the Association of UK Course Measurers (AUKCM) has found that the course used to initially calibrate the bike - The Middlewood Way in Macclesfield - was found to be short by 0.5pc, which means 33 races measured using this method could be declared too short.

So far, five have been re-measured and found to be too short - by between 0.2pc and 1pc.

The Macclesfield Half Marathon , which takes place in September each year, is among the courses yet to be remeasured, according to the AUKCM.

Others on the list are: Capesthorne Half Marathon; Arley 10k; Tatton Half Marathon; Macclesfield 5k; the Wilmslow Half Marathon; the Stockport 10 Mile Road Race; the Oldham Half Marathon; the Salford 5K and 10K; the Tameside 10K; and the Littleborough 5K.

An AUKCM statement read: “Following a re-measurement after complaints were received both from runners and the runbritain rankings of a short course being used for the Greater Manchester Marathon, a possible contributor to the short course was identified as the calibration course in Middlewood Way which was used to calibrate the bicycle wheel.

“An independent check, by a measurer having calibrated on an alternative calibration course, identified that the Middlewood Way course was short by 0.5pc.

“Accordingly we have identified courses which may have been affected.”

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UK Athletics has said it will not recognise times from the three Greater Manchester Marathon races from 2013, 2014 and 2015 due to the blunder which meant the course was 380m under the correct distance, affected around 24,000 results over the three years.

The problem was sorted in time for this year’s event, on April 10, thanks to a new course.

Mandy Calvert, Macclesfield Half Marathon race director, said they are awaiting 'further clarification' on any implications the measurement blunder may cause, but said no runners wearing GPS monitors had ever raised any concerns about the course being short.

She said: "The Macclesfield Half Marathon committee are aware of the reports of potential errors in the official measurement of some races in the North West and are seeking further clarification on the implications for the Macclesfield Half Marathon and 5K.

"Our races were last officially measured in 2013 and 2012 by the Association of UK Course Measurers.

"We have never been made aware by runners that the courses have been recorded as short on their GPS traces. However, the committee will be taking appropriate action including having the courses re-measured, and have every confidence that our races meet all the necessary standards."

She added: "As the races start and finish on the athletics track we are able to make adjustments to the course length by changing the distance that the runners run on the track at the start and finish of the races, therefore we do not anticipate any major changes to the race routes whatever the outcome."

Nick Bishop, who helps organise the Waters Wilmslow Half Marathon, which took place in April, says he is confident their course distance is accurate as it has been measured within the past 10 years.

He said: “There is a suggestion that some North West races need looking at. Having spoken to the UK course measurer we are as confident as we can be that ours will come up accurate.”