Les Trumpeter, the Tory candidate for Hateley Heath, claimed plastic boards were fixed to lampposts with cable ties.
Mr Trumpeter has branded the move "hypocritical" after Sandwell Council declared a climate emergency last year.
The decision was taken by council chiefs last year as part of a bid to tackle emissions and the use of single-use plastic.
Mr Trumpeter said: "Plastic getting into our oceans is quite rightfully a major concern now. So it’s odd that a party that is trying to promote its green credentials is sticking up plastic posters tied to lampposts with single use cable ties."
Nicola Richards, MP for West Bromwich East, added: "A Conservative Council in Sandwell will ban the outdated lamppost posters from our borough, as in neighbouring boroughs.
"They’re an eyesore and in an increasingly environmentally conscious world they have no place in modern campaigning."
Les Trumpeter is running against Labour's Kacey Akpoteni, Reform UK's Jacqueline Nock and Independent Paavan Ohm Sehmar for the election on May 6.