A homeowner who built an "illegal" wall in his garden may have to take it down because it is blocking an ancient wildlife corridor used by hedgehogs.
Mohammed Ulhaq applied for retrospective planning permission but Peterborough City Council refused it.
The area near the wall - 6ft (2m) beyond the boundary of Mr Ulhaq's property in Grimshaw Road - is home to about 45 species of flora and fauna.
Councillor Chris Harper said it had "divided" the corridor into "zones".
Members of the Planning & Environmental Protection Committee voted unanimously against the retrospective application, the Local Democracy Reporting Service (LDRS) said.
The council had already asked Mr Ulhaq, who was not present at Tuesday's meeting, to provide "hedgehog holes" in the wall.
But Richard Olive, a member of a local action group against the abuse of planning rules, said the holes were "too small, infrequent and raised above the ground".
Mr Olive told the meeting: "Hedgehogs cannot climb, so what are the council proposing to do for them? Ladders and trampolines?
"The wall should never have been built in the first place. It is an eyesore and illegal."
Liberal Democrat Christian Hogg said: "If we allow this retrospective planning application to go ahead, what possible objection could we have if every household on Grimshaw Road decided to land grab 2m to extend their gardens?"
Committee chairman, Conservative Chris Harper, said: "This wall has effectively divided the wildlife corridor into two different zone that the creatures who use it now have to try and navigate."
"Clearly this is an important precedent that we are faced with, and I would be happy to delay the decision today for the wildlife officers to go back and survey the verge more carefully."
Mr Ulhaq must now decide whether to appeal the decision, or face a possible demolition order from the city council.