Celebrities courting the paparazzi one minute and taking legal action the next means photographers "don't know where they stand", the Leveson Inquiry has heard.
Darryn Lyons, the founder of photo agency Big Pictures, told the inquiry into press ethics that celebrity photographers are left in an "extremely ambiguous" position by publicists.
"Any sort of legal action is concerning, especially like situations where one day we will come for a picture with Naomi Campbell, which has been set up through her PR people, and then on the next she is sending through some kind of legal action for privacy. It's the same with the singer Charlotte Church," Lyons said.
"That's the whole problem with the industry - picture agencies and photographers don't know where they stand.
"For example, Lily Allen: you will photograph her on a beach and never hear a thing because they are lovely pictures and the next time you will get a legal letter through the post.
"There are publicists and stars taking cash through photographs by the paparazzi on a regular basis," he added.
He said that publicists for stars such as Maria Carey and Paris Hilton will tell Big Pictures exactly where celebs are and where they will be staying during their time in the UK.
"It's an extremely ambiguous situation," he said. "Picture agencies that are courted by celebrities don't know what's right and what's wrong because the common practice of the last five or 10 years has changed dramatically, with a kind of back-door privacy law."
Lyons told the inquiry that photographers would value greater guidance on the lines between public and private. The bad reputation of the paparazzi has been partly created by the celebrities who use them for publicity.
"The paparazzi are regularly used by publicity agents to boost someone's profile. It's all over the place in the UK as to what [picture agencies] can and can't do.
"It's wrong, considering how much celebrities use these situations for their own self-gain on a regular basis."
Carine Patry Hoskins, a member of the inquiry, questioned Lyons on whether he believed that his Mr Paparazzi website, which collects celebrity pictures from amateur photographers, could be seen as encouraging the public to intrude on celebrities' privacy.
Lyons stressed that photographers were encouraged not to intrude and added that pictures were assessed on how they had been taken before they were used.