The jobs will go after Derbyshire County Council approved an £8.6m cut to its early help budget.
The budget reduction will take effect over the next five years - including a three-year transition phase - dropping from £12.9m in the current financial year, to £4.3m by 2023/24.
Under the approved plans, services currently providing family support to around 4,000 children and their families will be cut back and focus, as a council report states, "on those who most need help to prevent harm to children, reduce family conflict and breakdown and to help parenting and family functioning".
Schools, health and voluntary organisations will be expected to step in to replace the less-targeted early help offer.
This part of the structure will be developed under the guidance of a transition team set up by the council to help deliver services and identify external funding sources.
This team will receive £1.3m per year for three years.
The changes will see the council end all funding to generic youth activity clubs, such as drop-in groups, and instead focus on individual and peer-support groups helping the most vulnerable teenagers.
It will also provide grants and support to encourage community leaders and parents to set up youth activity groups.
The Conservative-run council will also end its provision of careers information, advice and guidance for 14- to 18-year-olds, only retaining support for young people aged 16 to 18 who are not in education, employment or training.
The council confirmed that 160 full-time equivalent posts would be lost as part of the changes agreed by cabinet on 31 January.
However, official numbers have been questioned by a local trade union representative, who said he was prevented from scrutinising relevant council papers on the basis of confidentiality.
Neil Ploughman, Unison branch chair and senior convener for children's services, said a 65 per cent cut to the budget could mean a 65 per cent cut to staff, which in a team of around 470 meant potentially more than 300 could be in line for redundancy.
"We have no idea of the exact figures," said Ploughman. "The cabinet restricted the papers, even when we offered to sign confidentiality disclaimers."
Ploughman said morale among early help workers was "on the floor" as a result of them facing three service redesigns in the past five years.
In 2016, the council cut its children's services budget from £127m to £90m, and again by £68m by 2019.
Some schools have already been working in clusters to hire early help staff to deliver services, said Ploughman.
But he warned that many schools were already struggling, following a £12.9m cut in the local schools funding formula.
Responses to a public consultation in October last year showed high levels of dissatisfaction to the proposals.
Sixty per cent of the some 500 respondents said they "strongly disagreed" with plans to target support to those most in need, and deliver services from schools and health providers.
Some 66 per cent opposed the plans for changes to youth services, and 49 per cent strongly disagreed with proposals to reduce the way it provided careers services.
"There was concern that schools/NHS/voluntary groups don't have capacity or funding to take on additional work caused by the proposed scaling back of Derbyshire County Council's family support services," stated a council summary of the consultation responses.
Ruth George, Labour MP for High Peak, Derbyshire, said the cuts would mean thousands of families and children at risk would miss out on the support they desperately need.
"Much of the burden will fall on schools who had not been consulted when I wrote to inform them of the proposals," said George, adding: "It will be especially difficult for smaller schools and those with high levels of children at risk to organise the support needed.
"If just a handful of those children need to be taken into care because of the lack of support, it will end up costing the council more."
The council claims it is attempting to mitigate impact on staff, including by offering internal employment opportunities, voluntary redundancy, retraining opportunities and support sessions.
A spokesperson said: "Changes to the early help service would not be fully implemented until the end of the year and most importantly, families currently receiving early help would continue to be supported in the same way as they are now to avoid disruption.
"The funding is still in the service - the change is in who will deliver it (e.g. partners including health, schools etc) and how it is delivered."
Derbyshire's cabinet member for young people Alex Dale, said the new approach intended "to strengthen our communities and give families the confidence to know that while we would still be here to help when necessary".