The group parked 17 caravans on land next to the Agricultural Business Centre a fortnight ago after being evicted from another site nearby.

They moved on this week leaving behind a substantial clean-up operation and possible court action.

Warren Slaney, head river keeper at the Haddon Estate, said: "We have two private prosecutions pending at the moment for use of illegal instruments in the river and we are determined to pursue those prosecutions where others have just let them go.

"All the fish in the river are wild and coming towards spawning time so any disruption to them is unwelcome.

"We have seen the travellers removing fish from the river and taking them back to the caravans. The Crown Prosecution Service have not pressed charges so we are going to pursue a civil action.

"They have to be shown that they cannot just ride roughshod over people."

Council staff worked on the site during the weekend and were also forced to tour the area cleaning up tree clippings after the travellers went door-to-door offering a conifer cutting service and then fly-tipped the waste.

A spokesman for Derbyshire Dales District Council said: "The team had to clear away around ten tonnes of conifer branches from half a dozen sites across the region."

District council leader Cllr Lewis Rose said: "We would encourage Dales residents to act responsibly when approached at their doors by people offering a conifer-trimming service.

"While they may be satisfied with the job that has been done, I would hope they will now have concerns about the way their waste has been dumped around the Dales."