Dorset Council is reminding employers that school-age children must have a valid work permit before starting a job.
The warning comes as part of Child Employment Month in April.
The council says it is the employer’s responsibility to apply for the permit, which is free but can take up to three weeks to process.
The rules apply to young people aged 13 up to the end of Year 11.
Officials say the system ensures work is safe, appropriate and does not interfere with education.
Without a permit, young workers may not be covered by insurance if something goes wrong.
Clare Sutton says part-time work can benefit young people, but safeguards must be followed.
Employers who fail to comply risk prosecution and invalid insurance cover.
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