Heads will be allowed to view confidential HR records about teachers' previous performance before appointing, as part of Government attempts to end the recycling of "incompetent" members of the profession.
In future, all reports of appraisals will be available to school leaders employing a new member of staff.
Department for Education officials have said the change in regulations will stop the practice of heads providing good references for incompetent staff as part of a "compromise agreement".
Teaching and heads' unions have branded the reforms "madness" and "misguided and ridiculous".
They have warned that appraisals could become meaningless because teachers, fearful of not being able to get a new job in future, might not admit to failings.
The reforms, announced by education secretary Michael Gove this week, are designed to get rid of "bureaucracy" in the systems for dealing with poor teacher performance. Other changes allow heads to "remove poorly performing teachers" within one term. The changes will come into force from September.
"We want to do all we can to help headteachers and employers to make well- informed decisions about teacher appointments," says a consultation document on the changes.
"We propose that regulations should require employers (and former employers) to provide copies of a teacher's previous appraisal statements to a potential employer when asked by them to do so in support of an application for a teaching post.
"We believe this could helpfully supplement the information provided by references and may also have the effect of limiting the extent to which compromise agreements between teachers and employers can subvert the reference process."
The changes mean any head who provides a "dishonest or misleading" reference which does not "tell the whole story to another school" could face legal proceedings.
Association of Teachers and Lecturers general secretary Mary Bousted said the proposal to share appraisal records was "outrageous". She wants a meeting with Mr Gove to protest.
"This will completely distort the appraisal process; it will make it a charade. Teachers won't want to admit to needing any extra training," she said.
"This is so misguided and ridiculous, it's laughable - but we are not laughing. It shows a fundamental misunderstanding of what appraisals are all about. It's corrupted, iniquitous and wrong-headed and it will destroy professional development."
Heads' union the NAHT general secretary Russell Hobby supports the reforms overall, but told The TES that allowing employers to view appraisal records was a "single moment of madness".
"At the moment the danger is for bland references - this will create bland appraisals instead," he said.
Brian Lightman, general secretary of the Association of School and College Leaders, said there was not a "big demand" from heads to see appraisal records.
"It's been quite a surprise to see that proposal and we are considering the implications of this," he said.
"Appraisals should be honest and rigorous. Nobody should skirt around the truth and they should show how things really are.
"If everyone is aware someone else might see it then they might be less, or more honest - it could work both ways."
NUT general secretary Christine Blower said the changes risked "jeopardising the fundamental purpose of performance management, which is to engage in an open and respectful dialogue to assist teachers in the continuing development of professional skills".
KEY PROPOSALS: WILLING AND ABLE?
Abolition of many performance management regulations, including the number of hours heads are allowed to spend observing a teacher in the classroom.
Systems for performance management and capability proceedings will be scrapped, and replaced with a single "model policy", which will not be statutory.
Teachers involved in capability proceedings will no longer be able to stall action because they are on sickness absence or have made a grievance complaint about a colleague.
Original headline: Job applicants' appraisals are opened up to heads