An EU referendum voting guidance leaflet has been withdrawn after complaints it could influence voters’ decisions on 23 June.
Graphic instructions on how to vote included in material sent out with postal votes in Bristol showed a pen hovering over the remain box.
It was attacked as unfair by Brexit campaigners – who said similar pictures had been reported in other parts of the country as ballot papers begin to arrive.
The Electoral Commission said while the graphic was unlikely to sway voters, it “clearly shouldn’t have been used” in that form. A spokeswoman said the commission had acted to ensure the leaflet was replaced by Bristol city council and was investigating whether the issue was more widespread.
The council said about 47,000 postal vote packs had already been sent out, leaving only about another 5,000 that would include a revised version.
Vote Leave’s national organiser, Stephen Parkinson, said: “It is completely unacceptable for official guidance from local councils to appear to tell people which way to vote. We have contacted the Electoral Commission to find out how many ballot papers might have been influenced in this way, and to ask them to take urgent steps to correct it.
“With the full weight of the government machine campaigning to keep us in an unreformed EU, it’s all the more important that local authorities and the Electoral Commission show that this referendum is being conducted fairly and impartially.”
A Bristol city council spokesman said: “This form is designed to explain the logistics of voting by post and not to suggest how someone should vote.
“The placement of the pen graphic was entirely incidental and we do not believe that anybody could reasonably be influenced by such a graphic. However, given current sensitivities, for all future postal vote dispatches the form and graphic will be amended.”