The father of two children snatched by their alcoholic mother is appealing for the public's help to trace them amid fears she may have fled the country.
Tamara Dyson, 37, snatched the twins, Vixen Rae and Billy Blu Francis, from a contact centre in Skegness on Thursday afternoon and they have not been seen since.
The children were "at serious risk of harm", a judge sitting at Lincoln County Court said, adding that they may have been taken to the Republic of Ireland.
Judge Heather Swindells said: "Both Vixen and Billy were in foster care because of concerns about Tamara Dyson's ability to look after them, particularly as she has a chronic and dangerous alcohol problem.
"This is the second time in a week Tamara Dyson has removed the children from contact.
"It's the view of the court that the children are at serious risk of harm.
"Despite the best efforts of the police since Thursday the children have still not been found and there are concerns that Tamara and the children are no longer in the country."
Because of concerns about the children, Judge Swindells took the unusual step of issuing an order under the Children Act 1989 allowing the care proceedings in the case to be reported.
The twins' natural father, 31-year-old Billy Francis, an electrician from Greenwich, London, pleaded for the public's help to find the youngsters.
He said: "I have been having contact with the children on a regular basis every week which has been going well.
"I last saw them on the morning of May 20 and I was shocked to be told later that afternoon that they had been taken by their mother.
"This was the second time that she had done this. On Monday she had taken them without consent.
"I am livid that this has happened with social services while under their care and responsibility."
The children were taken from Roseberry Avenue Contact Centre in Skegness. They were in foster care while their mother lived at Firbeck Avenue in the resort.
Mr Francis said he met Ms Dyson 10 years ago and in 2006 they had the twins. They split two years later and Mr Francis blames her addiction to alcohol for the break-up.
He said that when the children went missing for the first time last week, he phoned round every number in his phone book before tracking Ms Dyson down to the home of a 90-year-old retired schoolteacher in Skegness.
Mr Francis added that social services told him Ms Dyson managed to take the children while they were distracted making a cup of coffee.
He said: "Tamara is just not stable at the moment. She is drinking heavily and I am worried to death.
"She's a very distinctive woman and she has two kids with blue eyes and blonde hair with her. The kids are my life. I love them to death, I can't describe it any other way. I just haven't got a clue where they have gone."
Detectives at Lincolnshire Police said they believed Ms Dyson and her two children left the contact centre on Roseberry Avenue on foot but might have got into a car nearby.
In a statement, police said: "This may not have appeared out of the ordinary but we are anxious for anyone who was in that area of Skegness at the time to come forward and contact us."
Detective Inspector Andy Wardell added: "This information does not alter the police investigation as our paramount objective has always been the safe return of the children.
"Consideration needs to be given to Tamara Dyson's character and the direction this may take the inquiry. However, we can confirm that no information has been received to suggest the children have suffered any current harm.
"The risk to the children and to Tamara remain high and inquiries involving liaison with other police forces and partner agencies continue."