Cleethorpes beach and Humberston Fitties both currently have pollution warnings from sewage recently being discharged in the area.
It comes after Conservative MPs rejected a bill which would have attempted to limit how much waste would be allowed to overflow.
MPs for Grimsby, Cleethorpes and Scunthorpe joined the majority of Conservatives in rejecting it.
Overflows into rivers are supposed to be “exceptional circumstances”, but data from the Rivers Trust reveals it happened nearly 1,000 times in northern Lincolnshire last year.
Conservatives argued that the amendment would have meant that sewage could potentially backup into streets or houses instead.
The group Surfers Against Sewage monitors the water quality of beaches in England.
The current alerts it has issued say: “Storm sewage has been discharged from a sewer overflow in this location within the past 48 hours.”
Sidney Sussex ward councillors Debbie Rodwell and Marie Green say that there is “nothing more important than our water supply”, and have urged MPs to stand up for the area.
“As a councillor who represents Sidney Sussex a coastal ward, we would like to speak out publicly about my shock and disappointment that our local MP’s are not standing up and protecting our water system,” Coun Rodwell said.
“Cleethorpes has the Blue flag and when Labour were in administration we were very proud of that. We don’t want to lose it and we definitely don’t want to see or hear that raw sewage is in the Humber or anywhere else in fact.
“As the world is coming together to hopefully try to protect the environment it really doesn’t make sense this is allowed to happen.
“There is nothing more important than our planet and water supply. The water companies and government need to sort this out now and our local MPs should be standing up for our area in this issue.
“At a time when the world is focusing on environmental issues and even the Royal family is speaking up I think we need to do everything we can to ensure we keep and improve upon our environmental standards.”
Three MPs from the Grimsby and Scunthorpe area opposed to amendment, and one did not vote either way.
Great Grimsby MP Lia Nici and Cleethorpes MP Martin Vickers voted against the protections.
Scunthorpe MP Holly Mumby-Croft also opposed it.
Brigg & Goole MP Andrew Percy did not vote.