Department for Education data released by children's minister Robert Goodwill reveals that between 2014 and 2017 there were around 600 more 19- to 21-year-old care leavers classed as Neet.
The figures, which were revealed in response to a parliamentary question by Labour MP Ian Austin, show there were 10,870 19- to 21-year-old Neet care leavers at the end of March 2017, compared with 10,250 at the end of March 2014 - a rise of six per cent.
There has also been a 7.5 per cent rise in the number of Neet care leavers aged 17 and 18 since 2016.
While at the end of March 2016 there were 3,060 care leavers in this age range classed as Neet, this had risen to 3,290 by the end of March 2017.
According to looked-after children statistics released last month by the DfE, 31 per cent of 18-year-old care leavers were Neet, compared with 12 per cent of all 18-year-olds.
Children's charity National Youth Advocacy Service (NYAS) is urging more employers to give opportunities to young people leaving care.
"Young care leavers are not going on into work, education or training and that is a problem we have to act upon," NYAS chief executive Rita Waters said.
"We want employers to give children leaving care more of a chance and to make sure they have a guaranteed job interview or access into further education.
"We know there are some fantastic schemes like bursaries and apprenticeships already out there but more needs to be done to make sure these fantastic, talented young people get the start in life they deserve.
"That's why we want to make sure the government continues to assist them into education, training or into work."
A DfE spokeswoman said: "Our reforms are ensuring that care leavers have the support they need to make a successful transition from care to independence.
"Despite an increase in the number of care leavers, the proportion not in education, employment or training has remained relatively stable. But we know we need to go further to ensure we continue to help people fulfil their career goals and ambitions."