Clean water campaigners have said two beaches in Devon should be stripped of Blue Flags because they do not meet emergency sewage warning standards.
Surfers Against Sewage (SAS) said Bigbury-on-Sea and Challaborough beaches did meet standards for public warnings over 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, of Keep Britain Tidy, 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 its 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 required beach operators to warn the public during and after an emergency pollution event, such as a sewage discharge from a combined sewage overflow, SAS said.
Bigbury-on-sea and Challaborough are two among 35 around the UK SAS said it had identified as failing to do this.
It said it was because the beaches' owner 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."
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."
Devon received 12 Blue Flags for its beaches earlier in the year.