Police are targeting two young sisters in the hunt for their fugitive father Mark Acklom who is on the run with them in Europe.
Detectives are concerned for the girls' emotional welfare and are urging the public to try to identify them.
Officers believe the key to tracing conman Acklom , 44, is to find the school where his children are registered.
Acklom's two daughters, aged eight and six, are likely to be registered at an international school, probably in Spain, where they have grown up with their Spanish mother.
Police also believe the girls' mother, Acklom's wife Maria Yolanda Ros Rodriguez, 47, is helping her husband avoid capture.
He is wanted for allegedly fleecing a British woman of her life savings after promising to marry her.
Detective Inspector Adam Bunting, of Avon and Somerset Police, said: "We believe Acklom and his wife are in the company of their two daughters, girls aged eight and six. We believe they will be enrolled at an international, fee-paying school on the continent."
The girls were suddenly removed from their private school El Limonar in the village of El Palmar near Murcia a year ago, when Sky News revealed that their father was about to be added to the Most Wanted list.
DI Bunting said: "They've been uprooted away from their family, away from their friends, away from their school overnight. They didn't have a chance to say goodbye to their friends.
"As they are living on the run with their father, who is a wanted fugitive, we have significant concerns for their wellbeing."
Acklom, who uses the name Marc Ros Rodriguez and other aliases, is the subject of a European arrest warrant and is on the Crimestoppers and National Crime Agency's Most Wanted lists.
He is wanted for fraud, an alleged romance scam on Carolyn Woods, who was running a boutique in Gloucestershire when Acklom met her in 2012.
Ms Woods said he told her he was a wealthy Swiss banker and MI6 agent, and promised to marry her during a year-long romance, during which he duped her into lending him her life savings of £850,000.
At the time Acklom pretended to be commuting daily from Zurich, but was apparently living nearby with his wife and daughters.
Ms Woods, now aged 58, said Acklom left her destitute and emotionally wrecked and she considered suicide.
Acklom has been spotted once in his year on the run - he was photographed at the terrace table of a cafe in Geneva, Switzerland, in May. He was sitting chatting to a Spanish fellow fugitive, Jose Manuel Costas Estevez.
Police say Acklom is probably in Spain, where he has lived in the past, but is fluent in several languages and has connections to Italy and Ireland. He could have travelled outside Europe.
His wife has been involved in various property companies, sometimes with her husband, and she may be working as a yoga teacher or attending yoga classes, officers say.
DI Bunting said: "We don't think she has committed any crime, but I have no doubt she is aware of his fugitive status and is willingly travelling with him and their children.
"We want ex-pats with children in international schools to let us know if they have noticed the recent arrival of a family with two young girls. The family will appear to be Spanish, but all speaking good English."
:: Anyone in the UK with information is urged to call, anonymously, the Crimestoppers charity on 0800 555 111, or from Spain dial 900 555 111. Information can also be passed online at the website www.crimestoppers-uk.org .