Substandard teachers could be eased on to the upper pay scale in September 2010 without having to improve their performance, a pay expert has warned.
The way teachers progress to the upper scale is being overhauled from this September.
Previously, when teachers applied to advance from the main pay scale, they had to provide evidence of how they met a series of conditions.
Now, the onus is being put on heads to gather evidence through performance management reviews.
When teachers apply, heads are supposed to reach a decision by examining the two most recent reviews.
But concerns have been raised that many heads have failed to gear reviews to this process.
Nigel Middleton, director of consultancy Head Support Ltd, which has worked with more than 1,000 schools over the past year, said heads were unaware of their new responsibilities.
"The whole situation is pretty chaotic," he said.
"Teachers who reach the top of the main pay scale this September can apply to join the upper scale from September 2010.
"Many heads have not carried out checks over the past year to see if those teachers are ready. They will have little alternative but to put them through the threshold," he added.
"That could be good news for teachers, but will lead to a lot of unhappy heads, who are under massive pressure not to move people who aren't terribly good on to the upper pay spine."
Mr Middleton, an ex-head, added: "We hear about crackdowns on underperformance and MOTs for teachers, but a golden opportunity to make the threshold a more rigorous procedure has been missed."
There is no exact figure for the number of teachers currently at the top of the main pay scale, but it is thought to be up to 20,000.
Mr Middleton said that the majority of those who apply to join the upper pay scale are good teachers who deserve the extra pay.
Stephen Szemerenyi, pay and conditions consultant at the Association of School and College Leaders union, said heads faced with insufficient evidence would not move teachers straight on to the upper scale.
Teachers have the whole academic year in which to apply, so most will want to delay their application until their most recent performance can be taken into account, he said.