A rail firm has been accused of using "Arthur Daley" tactics to sell cut-price travel tickets.
More than 200 flyposters were put up on railings, road islands and around Brighton Station last weekend advertising a four-for-two ticket offer by Thameslink.
Officers at Brighton and Hove City Council raised the alarm when they spotted the posters, featuring four young people planning a day out, being put up and quickly ordered them to be removed.
The company immediately complied but insists it wasn't breaking any law.
Now it has been warned a repeat of the sales tactic could result in prosecution.
Chairman of the council's environment committee Councillor Chris Morley said: "These big companies ought to know better. For a supposedly responsible organisation like Thameslink to resort to these Arthur Daley tactics is not acceptable."
The poster appeared all over the city last weekend as part of the Thameslink promotion.
Many were attached to boards and tied to city centre railings along roads and traffic islands as well as around the station.
Coun Morley said: "They can afford to pay for legitimate advertising. Instead they resort to disfiguring prominent parts of the city.
"They've been warned. If it happens again, we will prosecute them."
But Thameslink reacted angrily to suggestions it had used dodgy tactics to market its special offer.
Spokesman Martin Walter said: "I think the council is entitled to its opinion but it was part of a proper campaign. There was nothing wrong with the posters and they were well finished off.
"We asked our distribution company to erect them around places where young people go, like clubs and bars. There is nothing Arthur Daley about it. It's perfectly acceptable."
Mr Walter said Thameslink understood the law to mean it was legal to put posters up but if a council asked to have them taken down then they were obliged to do so within 48 hours.
He added: "The distribution people who handled it had clear instructions that the posters were to be put up around these venues because that was the market we were aiming at."
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