Image caption Not all teachers are happy in their work, the NASUWT survey suggests

UK teachers are increasingly dissatisfied and many have considered quitting, a union survey has suggested.

Government reforms to pay and pensions, a heavy workload and school inspections were a source of concern, the poll of 14,847 members of the NASUWT suggests.

The findings come as the NASUWT and the National Union of Teachers (NUT) in the north-west of England prepare for a one-day strike on Thursday.

The government said more top graduates than ever were coming into teaching.

Under the government's changes, due to come into effect in England and Wales from this autumn, teachers' pay will be linked to performance in the classroom, with schools setting salaries, rather than following a national framework.

The NASUWT survey found more than half of respondents (53%) felt their satisfaction with their job had fallen in the past year - up 6% compared with those questioned in 2011.

Our reforms are giving schools more freedom and allowing head teachers to reward the best teachers Department for Education

Almost two thirds (65%) had considered leaving their job in the past year, while more than half (54%) had considered leaving teaching entirely, the survey claims.

It found that teachers' top four concerns about their jobs were workload (chosen by 78%), followed by government changes to pensions (51%), pay (45%) and school inspections (41%).

Chris Keates, general secretary of the NASUWT, said three years of "relentless attacks" on teachers by the coalition government had resulted in a profession in crisis.

"Teachers' pay and working conditions are inextricably linked to the provision of high quality education for all children and young people - yet the Secretary of State arrogantly and recklessly continues to cut pay, plunder pensions and hack to pieces national salary scales.

"Not content with this, he is now laying plans to remove other key contractual provisions, particularly those which support and enable teachers to work effectively. If these proposals see the light of day, teachers' holidays, working hours and other contractual provisions will be at the whim of employers and schools.

"No-one, therefore, should be surprised that over half of teachers are considering leaving teaching altogether."

'More freedom'

But a Department for Education spokeswoman said more top graduates and professionals than ever before were coming into teaching and vacancy rates were at their lowest since 2005.

"Our reforms are giving schools more freedom, ensuring we have an education system that matches the world's best, and allowing head teachers to reward the best teachers. These are surely ambitions the NUT and NASUWT should be supporting.

"We are very disappointed that the NUT and NASUWT have decided to take strike action, which less than a quarter of teachers actually voted for. Industrial action will disrupt pupils' education, hugely inconvenience parents and damage the profession's reputation in the eyes of the public at a time when our reforms are driving up standards across the country."

The industrial action in the north-west of England on Thursday is the latest move in the NUT and NASUWT's campaign over changes to pay and pensions.

The unions estimates 2,765 schools in 22 authorities in the north-west will be affected by the walkout.

A rolling programme of regional strikes has been arranged over the next few months, affecting schools across England and Wales.

The action is likely to be followed by a national walkout in the autumn.