Free weekly running sessions across Norfolk could be put in jeopardy if charges are introduced.

Organisers issued the warning after a council near Bristol voted to become the first in the world to bill parkrun – a 5k timed run organised by volunteers - a fee for the use of its grounds.

The local authority claimed it was 'unfair' to expect non-running residents to pay for path upkeep.

Sheringham parkrun is one of 12 parkruns in Norfolk which between them attract more than 2000 runners every week. And it revealed it would struggle to survive without the support of its hosts, the National Trust.

Janet Acott, who helps organise the event at Sheringham Park, said: 'I'm biased but parkrun is a wonderful thing and it's vital to keep it free and accessible for all.

'Our relationship with the National Trust is invaluable. I believe we both benefit from it. I think our involvement raises their public profile and many parkrunners staying on for coffee afterwards. Some come to run and then think: 'You know what, I'm going to come back with my family for a nice walk'.

'We work together and adapt courses depending on wildlife movement. We have our usual route and an alternative route when toads and frogs are migrating.'

But she added: 'Allowing us to park for free on a Saturday morning, up to 10.30am, makes a huge difference to people's ability to take part.'

The National Trust, which also hosts an event on the Blickling Estate, revealed it has no plans to charge parkrun a fee for the use of its grounds.

A spokesperson for the conservation organisation said: 'The National Trust has no plans to ask either parkrun or parkrun participants to pay to use our sites, except where ordinary admission prices or car parking charges apply.

'National Trust places host 25 parkruns and two junior parkruns, with more being planned. At our places in Norfolk, we currently welcome parkrun events at Sheringham Park and Blickling Estate.

'These weekly 5km timed running events are open to everyone, free, safe and easy to take part in. The events are organised by parkrun, a not-for-profit organisation, and their team of volunteers.

'They have proven a huge success at participating National Trust properties, encouraging people of all abilities to take part - from the novice runner to the more experienced athlete.'

For more details, and information on other parkruns in Norfolk, log on to www.parkrun.org.uk