A probe has been launched after more than 100 "restricted" statements from police officers and forensic experts were discovered lying in a giant bin at Farington Moss recycling centre near Leyland.

They reveal personal details about suspects and witnesses linked to Operation Montrose, run by Merseyside Police from 2004, which led to 59 drug traffickers being locked up for a combined 340 years.

They detail how police seized items including brown powders, bundles of cash and mobile phones across the country.

The papers provide information linked to a Liverpool Crown Court case involving Liverpool gang leader Paul Hannon and eight others, including driver Terence Sims, of Clifton Avenue, Leyland, who is now serving a 16-year jail sentence.

HM Courts Service has vowed to investigate the shocking security breach after the files were handed to the Lancashire Evening Post.

A spokesman said: "HMCS takes data security extremely seriously and we will investigate all allegations of breaches or incidents."

The tip user, who asked not to be named, found the files in the cardboard recycling bin at the centre.

He said: "I was putting a bag of rubbish in the skip and ended up finding this report. I just lifted up a couple of files – there was a pile of them. It's clear they are not meant to be seen by Joe Public."

As well as statements by police officers, the documents include details of surveillance on suspects at locations such as Bournemouth Airport and Liverpool John Lennon Airport, accounts of arrests and raids, allegations surrounding the doping of racing pigeons and a list of 707 exhibits used in the court case.

These include various photographs, video footage, passport details, mobile phones – including one mobile number – address books, cocaine, cars and thousands of pounds in cash.

Simon Davies, director of Privacy International, said: "This incident is a monstrous assault on privacy and a monstrous assault on trust.

"Whoever was responsible should be dealt with publicly to restore trust."

South Ribble MP David Borrow said: "It disturbs me and I would be interested to see the result of an investigation if the procedure was wrong.

"The bottom line is if there are papers that give a large amount of personal information and alleged offences, there should be rules in place that they are shredded."

Peter McNaught, district prosecutor for Preston Crime Prosecution Service, said: "When we prepare such papers we are obliged to provide a copy to barristers, the defendant's solicitors, the court, and numerous other parties.

"All case materials stored by the CPS are kept for a specified length of time depending on the type of case and then securely destroyed.

"We employ an outside company to take away the documents securely and dispose of them."