The historic railway runs along the seafront between Norfolk Gardens and Mewsbrook Park and is much-loved by local families and visitors.
But it has recently been targeted by vandals ‘who are spoiling it for everyone’.
“It is frustrating and makes us feel angry,” said Geoff Bashall, a volunteer for the Littlehampton Heritage Railway Association (LHRA), a charity which operates the railway, in association with Arun District Council.
“We are facing a constant battle with vandalism and interruptions.
“We are dealing with a small minority of people who seem to think it is rather amusing.”
The retired 72-year-old said protective fences were ruined a few weeks ago and when trains were running during the last weekend of June, vandals ‘decided it would be funny to put a portable road sign on the track’.
This meant the driver had to do an emergency stop with 50 passengers on board – putting everyone at risk, he added.
Geoff’s wife, Yvonne, 62, said it has been sad to see her husband come home depressed by it all.
“It is just soul-destroying,” she added.
“This jewel in the crown for the park has been resurrected from its run down state by a band of dedicated volunteers who give up their precious time to provide magical train rides for residents and visitors to our town.
“These volunteers work tirelessly improving the facility for us all.”
She urged people to be aware of any suspicious behaviour and to report it to the police.
A district council spokesman said: “Arun District Council fully supports Littlehampton Heritage Railway Association and we join them in condemning the vandalism, nuisance and dangerous actions which are affecting the safe operation of this popular service.
“We are working with the LHRA and the police to tackle these issues and would urge the public to report any incidents of anti-social behaviour and vandalism they witness.
“Incidents can be reported by calling Sussex Police on the non-emergency 101 number.”
A spokesman for Sussex Police confirmed officers were aware of anti-social behaviour at the railway.
“We were called over an obstruction on the line at Littlehampton Miniature Railway shortly after midday on June 27,” said a spokesman.
“The incident has been logged and the local PCSO has been informed.
“The Neighbourhood Policing Team is aware of ongoing issues of anti-social behaviour linked with the skate park, and there have been increased high-visibility patrols in the area.
“Any anti-social behaviour or criminal activity can be reported to us online or by calling 101.”