One tenth of the workforce at a Welsh Government-funded careers service is facing redundancy, according to Unison.
A total of 60 jobs at Careers Wales, which employs around 600, are to be axed, the union has said.
Careers Wales said it is facing a "budget shortfall" and "all options" are being explored.
The Welsh Government said it was aware Careers Wales was consulting on a "voluntary release scheme".
Unison said all employees of Careers Wales, which provides careers advice and information and is funded by Welsh ministers, had been written to asking if they would take voluntary redundancy.
The union said that, although Careers Wales' core funding for the year remained at £18m from the year before, the organisation was facing a £2.7m cut in overall funding for 2016-17 through the withdrawal of a fund that had prevented redundancies in the last financial year.
The Welsh Government said the fund was a one-off project actually worth £1.7m, and it was disingenuous to suggest extra funding had been withdrawn.
Jeff Baker, Unison regional organiser, said: "The government's plans don't make any sense."
"The Welsh Government hasn't concluded its strategic review with Careers Wales and by slashing funding to that organisation, it's forcing Careers Wales to sack people and its future is threatened.
"This is a ridiculous way to plan and fund a key public service."
Unison said Careers Wales staff numbers have halved in the last five years and it was making the staff cuts despite bidding to provide the Welsh Government's Employability and Apprenticeship training programme.
Richard Spear, chief executive of Careers Wales, said: "An anticipated reduction in our overall funding for 2017-2018 and a need to make further savings has resulted in a budget shortfall for the organisation.
"All options are being explored to address this shortfall.
"We will attempt to make the required savings via a voluntary early release scheme, in line with compulsory redundancy-avoidance best practice."
He said a 30-day consultation had started.
A Welsh Government spokesman said: "We are aware of Careers Wales' decision to initiate consultation on a voluntary release scheme and we hope and expect that Careers Wales, its staff and trade unions can work collaboratively on this issue to improve the long-term efficiency and financial sustainability of this important service."