Various cunning tactics have been employed to get items in.
John Attard of the Prison Governors' Association said: "It's not a fluke, people plan, they know the best parts of a wall to throw things over.
"There are all sorts of methods to get things over a prison wall. We've had people putting drugs in dead birds and sending them over with tennis racquets.
"We're talking about thousands of pounds worth of contraband but the criminals that are throwing them over are prepared to lose [part of] that to get some through."
While Pentonville prison in London only recorded 15 incidents of banned items being thrown over its walls in the last year, an anonymous resident insists "they've missed off a zero".
He said: "In the last year alone, I've seen it a good couple of dozen times myself.
"It tallies with the attitude of the prison. They will not hear reports of this going on. They don't want to know.
"It starts off on a Friday, and can happen all weekend. Around two o'clock in the morning is a favourite time. The prisoners will burn holes [in the perimeter netting] to fish out items that have been thrown in."
He added that items were attached to lines, thrown over the wall and pulled through holes in the netting by inmates.
Another prisoner who had been inside various jails over the last five years said this method was the most popular.
"They get thrown over the wall. If you go to any prison, walk the circumference of that prison, I guarantee you, you will see things hanging in the wires, there will be a parcel of phones hanging in the razor wire," he said.
"How are you supposed to control it? You can't stop it. There's no way of stopping it if everyone's doing it."
He explained that drugs are often hidden in innocuous items: "It can get thrown over the wall in tennis balls. They cut the tennis ball, fill them and throw them over. It's quite a military operation.
"I've seen it happen, balls flying over, people picking them up and they're going to the correct people."
Further inventive devices include juice cartons, tennis balls and shampoo bottles containing drugs and mobile phones, photos from the BBC have revealed.
But the Ministry of Justice is determined to tackle this growing problem, saying it "must do more".
"Those caught trying to throw packages over prison walls can now face up to two years in jail.
"However we must do more, which is why we are investing £1.3bn to transform the prison estate, to better support rehabilitation and tackle bullying, violence and drugs."