Campaigners battling to save a historic reservoir spillway have protested over works that have started at the site.

The Save Butterley Spillway group have accused Yorkshire Water of ignoring listed building status by carrying out work on the site.

Now they have called on Kirklees Council to investigate the erection of a metal platform and other works in close proximity to the listed Butterley reservoir spillway at Marsden.

They claim if it is found that listed building consent should have been obtained prior to undertaking the works, then Yorkshire Water could have acted unlawfully.

The company wants to carry out major repairs to the Victorian spillway to meet new safety standards but their plans have been rejected by the council following a huge outcry.

Yorkshire Water has lodged planning and listed building consent appeals against Kirklees’ refusals for its plans to replace the stone spillway mainly with concrete to upgrade it to current standards.

The Save Butterley Spillway group will be present at the public inquiry, expected to start on January 20, 2015 and will be putting forward the case that Yorkshire Water has not given sufficient weight to the heritage of the site.

The group will also be criticising Yorkshire Water’s design of the proposed replacement spillway.

A spokesperson for the Save Butterley Spillway group, said: “This potential breach of planning control illustrates that Yorkshire Water does not always follow proper planning processes. It has eradicated every last drop of any faith that the group had in the company in its ability to go about things in the right way.

“Further, given the poor quality appearance of the new structure that has been erected close to the spillway and Bank Bottom Bridge, which is also listed, it only serves to illustrate Yorkshire Water’s disregard for works to be in keeping with this stunning historical and landscape setting.”

A Yorkshire Water spokesman said: “This vital safety equipment was installed as an emergency measure after we discovered damage to one of our valves.

“This valve is important, as it supplies a local mill and also prevents downstream flooding after periods of heavy rain. We are having to keep water levels low in the reservoir until we can resolve the safety project that is subject to a planning appeal.

“We took immediate steps to resolve the issue and protect the safety of our operational staff.

“When we were contacted by the council about the work, we explained its urgency and asked whether the work fell within our permitted development rights as it is on operational land.”

The Save Butterley Spillway group urge people to write to object to Yorkshire Water’s proposals to destroy this unique and important historical spillway, which is the only listed water supply reservoir spillway in the country.

Objections should be sent to the Planning Inspectorate by September 10 quoting the reference APP/Z4718/A/14/2222372.