Tens of thousands of Romanian children are growing up parentless because their mothers and fathers are working abroad, according to new figures which raise questions about the extent and impact of large-scale migration on the eve of new EU rules governing Bulgarians and Romanians.

According to the Romanian ministry of labour, family and social protection, there are now more than 80,000 families in Romania in which both parents are working abroad while their child or children stay at home, with 35,000 more families in which one parent is overseas.

Those are just the official numbers; few parents inform the authorities about their intention to go abroad and many believe the real number could be significantly higher.

"This is a big issue for Romania," said Stefan Darabus, Romania director for the international NGO Hopes and Homes for Children, which runs programmes in the rural north of Romania to help children left behind by their parents. "In the cities and countryside, poverty and job opportunities take these parents overseas, but the children left behind are strongly affected by their absence."

"Those who grow up without the love or security of their parents are going to be negatively affected later in life," he added. In the southern Bucharest neighbourhood of Ferentari, one of the poorest areas of the Romanian capital, around two dozen young children sit in a classroom during lunch, colouring in pictures of fruit bowls and playing while a teacher looks on.

The children vary in age from five to 10 years old, but they all have something in common: they all have one or both parents overseas.

Cristina, one of the children, says her mother is in Spain looking for work. She has been gone a month this time already, but in the past she has been away much longer, she says. Her father is no longer in the picture. "Mum doesn't want to stay away long. She just went there to make money for me and my sister," said Cristina, a nine-year-old who lives with her grandmother when her mother is away. Many find themselves missing regular emotional or physical support as they grow.

"These children are in a very vulnerable situation, being deprived of their parents' affection, care and support," said Andreea Biji, a psychologist who works for Save the Children, which runs the classroom-based programme in Ferentari as well as programmes in 15 counties across the country.

Some Romanian parents have taken their children overseas with them, but for many this is not an option. "In France my husband earns €600 to €700 a month, which is a lot over here but not much over there," said Vasile Luminita, a 28-year-old mother of five whose husband has been working on a construction site in France for the last 18 months. "It is hard. Many times we have considered all moving but he stays in a very small room and sends the money back to give us a better life in Romania."

Luminita says the separation is hardest on her older children. "They understand the situation but it is hard for them always to see their father leaving," she said, cradling her two-month-old son, who has yet to see his father.

For some children in Romania growing up without their parents in their daily lives has come to seem normal.

Fourteen-year-old Amira Dumitru's mother left Romania when she was 11 months old to find work overseas. She now lives in Jordan and returns once a year to spend time with her daughters.

"I don't find it strange to grow up without parents [Dumitru's parents divorced before she was born, and her father lives elsewhere in Bucharest] – in my class alone there are three or four others like me," said Dumitru, sitting in the apartment she shares with her grandmother in the suburbs of Bucharest.

Dumitru says she is lucky, in that her grandmother raised her and her sister well and makes sure she gets good grades at school. When she is at the homes of friends who have both parents present she feels she is missing out on something, although she says she is not sure exactly what it is.

In recent years the Romanian government has tried to push through changes to better manage the situation of children left behind, especially those in more unstable environments. "Things have become better – there are now daycare centres where kids can be looked after and other support services," said Nicolae Gorunescu, the executive manager for the government child protection agency in Bucharest's District 6.

He said the government had recently introduced a law whereby parents not only had to register before going overseas to work but a judge had to approve of the chosen guardians. "The problem is a lot still don't tell the authorities that they are leaving. We have seen cases of teenagers being taken in by social services because they are fending for themselves, with just a few hundred euros sent home by their parents," he added.