Clean water campaigners have said three beaches in Cornwall should be stripped of Blue Flags because they do not meet emergency sewage warning standards.
Surfers Against Sewage (SAS) claimed Carbis Bay, Gyllyngvase and Polzeath beaches did not meet public warning standards for accidental pollution.
Keep Britain Tidy which manages the scheme said it would investigate.
South West Water said it was "disappointing for SAS to be irresponsibly raising unfounded fears".
Arwyn Jones from Keep Britain Tidy, which manages the Blue Flag scheme said: "What we're going to do now is cross-check the information and we will talk to each and every beach that they have named and validate whether their claims are right.
"If they prove to be founded then we will take appropriate action and if that means withdrawing the flag then that's what we'll do.
"We are determined to protect the reputation of the Blue Flag, and therefore we will act swiftly over the next few days and will take appropriate action if it's required."
'Real time' warnings
The Blue Flag programme is a worldwide initiative run by the independent non-profit organisation Foundation for Environmental Education (FEE).
One of its criteria requires that beach operators warn the public during and after an emergency pollution event, such as a sewage discharge from a combined sewage overflow (CSO), SAS said.
The beaches are among 35 around the UK SAS said it had identified as failing to do this.
It said it was because owners did not request real time information on such discharges and so could not warn the public during or after a discharge of raw sewage.
SAS said: "It is a major concern to SAS that these 35 beaches could have the Blue Flag flying whilst the public could unwittingly be swimming around in raw sewage discharged from nearby combined sewer overflows."
Stephen Baker, who owns Carbis Bay beach, said any threat to its blue flag could affect the area.
He said: "It would concern us because we wouldn't want to lose the Blue Flag. It is important to us and to Cornwall and its prosperity."
He added: "I'm not aware of any reported problems, and the public would be first to tell us if there were."
South West Water's operations director, Stephen Bird, said: "It's disappointing for SAS to be irresponsibly raising unfounded fears without realising the effect they may have on the region's number one industry - tourism - at a vital time.
"That's why we are already upgrading monitoring equipment at the locations which may affect these beaches named by SAS and spending money across the region investigating the many different factors which might affect bathing water quality in different catchments."
SAS did praise the work at Porthowan beach in which a sewage detector system has been updated.
In a statement Cornwall Council, which owns Gyllyngvase beach and co-owns Polzeath, said: "As SAS have reported, the Combined Sewer Overflow on the Blue Flag beach at Porthtowan has been upgraded with high tech monitoring equipment that alerts South West Water as soon as sewage discharges into the river and sea.
"The Environment Agency, Cornwall Council and Surfers Against Sewage are then provided with the information they need to warn the public."
The county currently has six Blue Flag beaches, including Porthmeor, Porthtowan and Sennen Cove.