The Government's new reading test for six-year-olds could face a boycott from teachers.
The National Union of Teachers (NUT) is expected to warn at their annual conference next month that the check is "unnecessary and inappropriate".
The union is due to discuss a motion which contains an amendment calling for a campaign against the test, including a ballot for a boycott if the results are used in league tables.
Ministers announced plans for the test at the end of last year amid concerns that children with poor reading skills were slipping through the net.
The test is based on phonics, a system which focuses on sounds rather than recognising whole words, and has been promoted by government as the best way to boost reading standards.
Pupils are asked to sound out or decode a series of words, some of which are made up, to test their reading skills.
The NUT's motion opposes the Government's claim that the check will raise reading standards and says that each child learns to read in a different way.
It says: "Conference asserts that the introduction of statutory testing of phonics for all Year One pupils is unnecessary and inappropriate.
"Conference maintains that there is no evidence that learning phonics 'fast and first' has a positive impact on children's long-term reading ability or enjoyment of reading."
The resolution says the test will have financial implications for schools, could lead to more teaching to the test and increase teachers' workload.
It calls on the NUT's executive to raise the union's concerns about the test with government and to highlight their worries to parents and the public.
An amendment also calls for the union to "prepare a campaign, including a boycott, should the Year One phonics check be used to contribute to any kind of league tables".
NUT general secretary Christine Blower said there were concerns that the test included "non-words" as well as real ones, and that the test was "decoding, it's not reading".