The man who threw acid over Katie Piper may have fled the UK two months ago, the Met Police have said.
Detectives are hunting for Stefan Sylvestre, 34, who is wanted on recall to prison.
The public have been warned he should not be approached.
Model and activist Katie Piper, 38, was severely injured and partially blinded in the 2008 attack after Sylvestre threw sulphuric acid into her face in Golders Green, Barnet, north London. She has gone on to campaign for burns victims, launch the Katie Piper Foundation and appear on Strictly Come Dancing and Loose Women.
The attack was carried out at the request of Ms Piper’s ex-boyfriend, Daniel Lynch.
Both men received life sentences, with Sylvestre given a minimum term of six years behind bars before his release in 2018, while Lynch was jailed for a minimum of 16 years.
He was convicted of ordering the attack and sexually assaulting the campaigner prior to it.
Sylvestre, whose last known address was in north London was released on licence - meaning he must obey conditions or risk returning to prison - but has now been recalled.
Met Police officers were notified on Friday, September 23, that he had been recalled to jail.
The force says enquiries undertaken so far indicate he left the UK on Tuesday, August 2.
Specialist crime command is working with partner agencies to locate and arrest him.
A Probation Service spokesperson has said: "We are urgently working with the police to bring the offender back to prison, where he'll face longer behind bars."
At the time of his release, the parole board said Sylvestre had “displayed empathy” and “expressed remorse and shame” for the attack.
Anyone with information on his whereabouts is asked to call police on 999 quoting CAD6239/23Sep.
Or to give information anonymously contact the independent charity Crimestopperson on 0800 555 111.