Senior figures in public service unions and in the Department of Finance have opposed the payment to ASTI members of a 4 per cent pay rise due next month.
The money, however, will be paid to 17,000 ASTI members on October 1st after the issue was considered by the Cabinet at its meeting in Co Donegal last week.
The 4 per cent payment is the final increase due under the terms of the Programme for Prosperity and Fairness (PPF). The payment is linked to progress in "modernisation", but finance officials believe that ASTI members have not delivered significant concessions on work practices.
Senior figures in ICTU also opposed the payment because ASTI withdrew from the PPF two years ago. The union also disaffiliated from congress at that time.
The Government decided to make the payment after a group of independent consultants found that the education sector had complied with the need for "modernisation" by agreeing to new school planning systems.
The Minister for Finance, Mr McCreevy, is expected to announce shortly that all public service unions have met the criteria for modernisation. This opens the way for some 280,000 public servants to receive the 4 per cent payment next month.
Last night, an ASTI source stressed that individual senior public service trade unionists - and not ICTU - had raised questions about the payment.
One, he said, was under the impression that ASTI had refused to co-operate with school planning but this was not the case.
Senior finance officials have been very hawkish in their approach to the ASTI. They believe the union's go-it-alone tactics of the past two years undermined public pay policy.
Senior figures in ICTU have also been furious with the union's approach. Some in congress take the view that ASTI has no right to expect PPF payments secured by other unions.
The ASTI has received all other payments under the PPF automatically. Part of the reason for this is the Government's reluctance to break the common pay scale, covering all three teacher unions.
Tensions between ASTI and ICTU come at a time when the union appears set on a more moderate course.
In the past month, the ASTI leadership has signalled its desire to end the current supervision dispute. The news, however, that some in ICTU opposed the latest payment could unleash protests from hardline ASTI members. It may also damage prospects of the union returning to the ICTU in the near future.