Leach, also known as Lee Cyrus, went missing from North Sea Camp open prison in Boston, Lincolnshire, on October 9, after going on day release.
The 47-year-old, originally from Preston, has previously admitted a string of crimes, including having sex with a 13-year-old girl, assaulting a woman and robbing a 90-year-old widow.
He spent 10 years on the Sex Offenders Register and children's charity NSPCC has warned he is at "very high risk of violent re- offending against children and adults".
Detectives are seeking him in connection with an incident in Perth last month.
A 23-year-old woman had been in bed in her property in the city's Bridgend area on October 15 when she was awoken by an intruder who threatened her with violence before sexually assaulting her.
Leach appeared on the wanted board of the Crimewatch programme, which aired on BBC1 last night.
The last confirmed sighting of Leach came from CCTV footage which shows him at a Barclays Bank cash machine in Nottingham city centre at 11.13am on Saturday, October 20.
Police have also released a new CCTV image of Leach on board a train between Preston and Nottingham on the same day.
Police then believe he caught a bus from Nottingham on October 20 to London but the latest unconfirmed sighting of him is in Preston.
Leach is described as white, around 5ft 11in, of stocky build with cropped hair and hazel eyes. He has a distinctive scar on his top lip under his nose and two distinctive tattoos, one with the name "Annette" on the bicep of his left arm and a figure of a barbarian woman on the back of his right shoulder blade.