The ASTI will tell schools next week not to implement an ambitious new science course, which is designed to arrest the alarming fall-off in students taking the subject.
The move represents a significant setback for both the Government and for industry, both of which have been seeking to revive flagging student interest in the subject.
It is understood that ASTI's executive, or standing committee, will shortly issue a directive advising members not to co-operate with the new Junior Cert science syllabus. This is due to be introduced in schools next week.
The ASTI action means that two separate Junior Cert courses in science will be examined in 2006, the old course and the new one.
Last night, ASTI sources said they had no choice but to take this action. "The Government has put this wonderful course in place but they have given us no resources to teach it".
ASTI members are incensed that the Government is attempting to press ahead with the new course, even though laboratory facilities in many schools are dilapidated.
Last May, the Minister for Education, Mr Dempsey, announced a series of grant supports for school to help modernise facilities. But ASTI sources say this is totally inadequate. Some laboratories, they argue, do not meet health and safety standards. The union also wants more in-service training for teachers before the course is introduced.
Mr Dempsey is determined to press ahead with the new course but the ASTI directive - in the name of general secretary, Mr Charlie Lennon - ensures it will not be offered in a majority of second-level schools. Schools have until the end of October to decide whether they will take the new or the old course.
The Department's grant package promised that labs in a poor state of repair would be given priority in the building programme. About 250 schools, said by the Department to require modest levels of work, can secure €3,500 per year. A grant of about €8,000 is available to a further 400 schools to help upgrade facilities.
The new syllabus requires students to perform and write reports on 30 mandatory experiments, but many schools are not in a position to teach these experiments because they do not have adequate science laboratories.
The old course, which concentrates on written work, has been severely criticised. It has been cited as one of the reasons why students are turning away from science subjects at Leaving Cert.
Only about one in seven students now take physics or chemistry at higher level in the Leaving Cert exam.
The recent report of the Task Force on Science recommended that a new, more modern course should be implemented without delay.
The other second-level teaching union, the TUI , is likely to introduce the new course.