MPs have urged that councils need to strengthen tracking 16 to 18-year-olds through education, employment and training.
It is a statutory duty for councils to monitor the activity of this age group, however a report by the public accounts committee says that data on up to 20 per cent of the youngsters in their area is "missing".
Nationally, that is 140,000 young people between the ages of 16 and 18, or a total of 7 per cent.
In the same report, it is claimed that lack of knowledge on these young people results in a lack of understanding makes it more difficult to target support towards those not in education, employment or training (Neet).
The committee has called for the DfE to urgently work with authorities to identify and share best practice on effectively tracking young people's participation.
Margaret Hodge, chair of the committee, said: “More than 100,000 young people are off the radar in that some local authorities do not know whether they are participating in education or training or not.
“If the activity of young people is unknown to the local authorities where they live, they are unlikely to receive targeted help.”
Councillor David Simmonds, chair of the Local Government Association’s children and young people board, said authorities could do more if they were granted greater legal powers to request information from other organisations.
“Councils are committed to identifying and supporting all youngsters to realise their full potential and have actually reduced the number of ‘unknown’ 16- to 18-year-olds by 14 per cent since 2012,” he said.
“To build on this success, councils urgently need more legal powers to ensure partners share vital information as quickly as possible.
“Too often the challenging task of reducing teenage disengagement is made far more difficult when schools, college, Jobcentres and national schemes do not provide the information needed to identify those in need of help.”
Latest government figures, published last November, show that the number of 16- to 24-year-olds who are Neet is the lowest it has been since 2007.
A DfE spokesman said: "The proportion of young people whose activity is not known by local authorities is decreasing.
"But we are not complacent. We continue to work with councils to encourage the exchange of good practice and regularly publish data on the progress made by each local authority so we and the public can effectively hold them to account for their performance."