Pippa Heylings, a district councillor and activist, will be the party’s candidate for South Cambridgeshire, a seat that has been Tory since the 1990s but which now has a majority of just under 3,000 votes.
The Lib Dems are hoping to change their fortunes by tapping into the anger residents feel about the amount of raw sewage being dumped into local beauty spots, an issue they claim is pushing voters away from the Conservatives.
The Blue Wall refers to Conservative strongholds in the south of England that the Lib Dems in particular are pursuing as Boris Johnson’s courts working class voters in the north’s Red Wall.
The first sign that the Tories’ armour had been dented by its new electoral strategy came when it lost Chesham and Amersham in Buckinghamshire to the Lib Dems with a 25.2% swing.
A key issue driving that loss was over proposed planning reforms, which have since been put on hold.
Heyling told HuffPost UK that voters in South Cambridgeshire had expressed “disgust” at the dumping of sewage into rivers such as the River Cam.
“This has always been one of the most environmentally aware kind of constituencies,” she said.
“We are one of the most water-stressed areas in the country, which means you’ve got environmental drought, and if you continue with the sort of abstraction and the pollution of the rivers as it is, then we’re in absolute crisis.
“It’s been a real issue on the doorstep, it is one of the things that I hear about most — one is a disgust at the dumping of sewage into the rivers, and then the other is about the threat to our chalk streams.”
She said voters in the constituency “feel they’ve been taken for granted” and pointed to recent gains for the Liberal Democrats, including in Cambridgeshire, where the Conservatives lost their majority for the first time.
The Tories are under fire in their traditional stamping grounds over a series of votes in the House of Commons regarding the discharge of raw sewage into rivers.
The House of Lords recently sought to add an amendment to the government’s environment bill, which would have imposed a duty on water companies to ensure that untreated sewage is not discharged into rivers.
A significant backlash ensued when the amendment was voted down by 265 votes to 202 votes, with some Tory MPs complaining of abuse on social media.
The government initially rejected the Lords amendment on the grounds that a legal duty to tackle overflows could lead to a bill of up to £600billion, which they said would have been passed on to the taxpayer.
The government was, however, still forced into a U-turn following the outcry, instead agreeing to a watered-down amendment that requires water companies to reduce the amount of waste they discharge into rivers.
Campaigners say the move still does not go far enough and will effectively still give water giants the green light to continue pumping sewage.
A Lib Dem source said there was “no doubt just how much the sewage vote has cut through in the Blue Wall”.
“The map of chalk streams in the country is actually near identical to Blue Wall constituencies. The Tories are completely out of touch with the Blue Wall if they think the sewage issue will go away anytime soon.”
The Conservatives have been approached for comment.