Almost half of young teachers expect to quit the profession within years amid a backdrop of increasing paperwork, longer hours and concerns over their mental health, a report has found.
The survey of just over 3,000 staff aged 35 or lower by the National Union of Teachers (NUT) found 45% did not envisage staying in the profession longer than five years.
Workload was the biggest concern (85%) for teachers, as well as a poor work-life balance (82%) and challenges brought about by changes to government initiatives (66%).
More than four in every five surveyed (83%) said that administrative tasks added to the workload without benefiting children in any way.
NUT general secretary Kevin Courtney said young teachers are at the "most idealistic stage of their career, perhaps".
He added: "But it is really disturbing that 77% have said their morale has declined.
"It's not just the question of the hours of workload, but the level of workload.
"The idea that the workload isn't even about educating the young people we work with is - we think - outrageous."
The majority of participants (59%) had been in teaching for less than five years, with more than half (50.5%) saying they work in excess of 56 hours a week.
Mr Courtney said: "The massive workload is stopping people coming into the profession, as well as increasing the losses we have from the profession.
"Young teachers are the future of the profession, yet many talented and enthusiastic professionals are being driven away from teaching to the detriment of our children's education.
"The Government needs to accept its responsibility in this crisis and take positive steps to resolve the issues behind the problems of teacher workload that are currently blighting the profession."
Teaching unions have previously warned that 98% of schools face a real-terms reduction in funding for every pupil over the next few years due to ongoing funding pressures, with an average loss of £339 per primary pupil and £477 for secondary students.
And despite protections on school funding, school spending per pupil has already faced reductions in real terms in many schools - with predictions from the National Audit Office that it is likely to fall by 8% by 2020.
Henry Emoni, a maths teacher at a secondary in Essex, said: "This is my fourth year in the profession and it's disheartening to see how frequently people leave the profession.
"We had a trainee teacher in a local school and the next day he was gone - only an email saying 'I don't think I can do this'.
"The reason? He said: 'I don't think I can survive.'"
Laura Chisholm, a science teacher at a secondary in Portsmouth, said just seven of the 37 people on her training course when she started teaching at the turn of the decade remain in the profession.
She added: "We should be left just to teach and provide awesome opportunities for learning.
"We end up filing endless paperwork, box-ticking, trying to prove we do our job. Maybe just trust us."