Convictions in 25 criminal cases where evidence was given by undercover reporter Mazher Mahmood are being re-examined, the Crown Prosecution Service has said.
The CPS said it had identified current and past cases where the "Fake Sheikh" was a prosecution witness following the collapse of the trial of pop singer and former X Factor judge Tulisa Contostavlos.
It said while past cases which resulted in a conviction were now being "considered", it had also offered no evidence in three live cases where the undercover journalist was a prosecution witness.
A CPS spokesman said: "We are now considering past cases which resulted in a conviction in criminal courts in England and Wales based on evidence provided by Mr Mahmood, and have identified 25 cases.
"As part of this process, over the coming weeks, CPS Areas will be contacting representatives of the defendants - or defendants themselves as necessary - convicted in these cases in order to provide them with a disclosure pack - details of material which they may consider undermines the conviction in a specific case."
Mr Mahmood, a former News of the World reporter, was suspended by the Sun on Sunday following the collapse of Ms Contostavlos's trial in July.
The former N-Dubz star went on trial after allegedly boasting that she could "sort out" cocaine for Mr Mahmood and put the reporter in touch with her rapper friend Mike GLC - real name Michael Coombs.
But both were cleared after Judge Alistair McCreath said there were "strong grounds" to believe Mr Mahmood lied in the witness box and "had been manipulating the evidence".
The CPS spokesman said today: "Following the halting of the trial of Ms Contostavlos and Mr Coombs, we took steps to identify current and past cases involving Mr Mahmood as a prosecution witness.
"We made it our immediate priority to carefully look into live prosecutions in accordance with the Code for Crown Prosecutors and any past cases which involved a defendant still in custody.
"There were no concluded cases where a defendant was still in custody, but we identified three live cases. Each case was looked at individually and no evidence was offered as we concluded that there was no longer a realistic prospect of a conviction."
Additional reporting by PAReuse content