A third of teacher training places unfilled in Wales
A third of secondary school teacher training places were not filled at the start of this academic year, official figures show.
A teaching union said it showed Wales is facing a problem with recruiting new teachers.
Only 553 students started initial secondary teacher training in September 2015 but the official target is 880.
The Welsh Government said the overall teacher vacancy rate "remains very low".
The Ucac teaching union said the figures were "dramatic" and blamed the "out of control" workload as one factor in making the profession less attractive.
Carmarthen West and South Pembrokeshire Conservative AM Angela Burns said: "With almost 40% of secondary school teacher training places not filled, these worrying figures further emphasise the deeply worrying recruitment problems faced in Wales.
"The new administration must place a greater emphasis on supporting teachers, with a renewed focus on continuous professional development, and giving the profession greater freedom and control."
Teacher training in Wales is currently provided by three centres involving five universities.
Each year, the centres are set recruitment targets for initial teacher training.
The all-Wales target for secondary teacher training courses starting in September 2015 was 880 but figures from the Higher Education Funding Council for Wales show only 553 places were filled - 37% below the target.
Recruitment to primary teacher training courses showed a slight drop in relation to the target.
Major reforms of teacher training in Wales are due to be introduced by September 2018.
Rebecca Williams, policy officer at Ucac, said she believed it was not pay and conditions in Wales which was the issue, but workload, which was leading to stress.
"The figures are beginning to tell quite a strong story that we have a recruitment problem into the teaching profession in Wales," she said.
"In a way it's just the tip of the iceberg, it doesn't take into account the drop out of those who don't finish the course and those who drop out in the early years in the profession because they find it's not what they wanted or it doesn't suit them."
The Welsh Government said it wanted to make sure the low vacancy rate continues with the "drive to improve standards and raise the status of the profession".
A spokesman added: "We are committed to recruiting individuals with the right skills, qualifications and commitment into the profession which is why training incentives are available in Wales to encourage high performing graduates to consider teaching as a career."