Cardiff Council has defended a series of advertisement banners displayed across the city, which invite people to attend church for Easter.
The banners read: "Trust in Jesus, he is alive, come to church," and feature the council's official logo.
They have drawn criticism from Humanists UK, who argue that the inclusion of the council's logo gives the impression that the local authority is endorsing a specific religion.
However, a council spokesperson said that it is not involved in "decisions regarding individual campaigns".
Humanists UK said it has received multiple complaints since the banners first appeared.
Wales Humanists co-ordinator, Kathy Riddick said: "Cardiff Council serves a diverse community with a wide range of beliefs.
"It has a responsibility to remain impartial and not give the impression of favouring or endorsing any particular religion or belief.
"By failing to make sure these banners clearly state they are paid advertisements from an external group, the council is using its authority and branding to promote one specific faith.
"We call on Cardiff Council to address the issue with urgency and then review its policies on lamppost banner advertising.
"Either it should make sure that all future adverts include prominent disclaimers regarding their origin, preventing any confusion with official council communications, or it should remove its own logo from the banners."
In a statement to Premier, a spokesperson for Cardiff Council said: "Under the terms of Cardiff Council’s Advertising Policy, registered charities and businesses are permitted to purchase banner space on council-owned lamp posts. The booking of this advertising space is managed by Bay Media, an external national provider of advertising space, in compliance with the council’s Advertising Policy.
"The Cardiff Council logo is placed at the bottom of all banner advertising coordinated by Bay Media in the city to demonstrate that the advert has permission to be on council property. It does not indicate any formal partnership or endorsement of the specific content of the advertisements.
"The booking of advertising space is an external process, and beyond setting the parameters of the overarching advertising policy, the Council does not take decisions regarding individual campaigns where they are compliant with the standards articulated in the policy."