The ATL teaching union has voted overwhelmingly to look at boycotting all tests at primary level.
Delegates at the union's annual conference in Liverpool voted 96 per cent for and 4 per cent against a motion to "explore a possible boycott of all tests at primary level".
The motion also called for the ATL executive to hold discussions "with both the NUT and NAHT to see if they would join such a boycott".
Jean Roberts, who proposed the motion, said: "The time has passed for moaning about tests. The time has come to put the nail in the coffin of testing."
The vote for a boycott came despite the government proposing last month to scrap key stage 1 Sats.
Ms Roberts said that while the government was "going in the right direction...without pressure it could slip back".
She attacked the government’s suggestion of returning to “failed baseline assessments”, and also criticised the fact that their consultation made no mention of KS2 Sats.
“Those will stay in place with the curriculum narrowed for so many pupils, as schools work to ensure they reach an ever rising bar,” she said.
Michael Carty, another delegate who supported the motion, said education was "in a pit" which was being dug by "the twin evils" of "test and league tables".
Teacher Rachel Murtagh said that her year four pupils were "already feeling the pressure" of KS2 Sats.