Teachers have to undergo the National Lottery-funded training to qualify for a pound;500 subsidy to buy their own computer.
Training is generally outside school hours.
Peter Scott, from the union's national executive, said the Computers for Teachers scheme could have provided n excellent opportunity to support the professional development of school staff.
Instead, he told the conference: "The Government's penny-pinching and greedy approach will seriously undermine it."
The TES has been campaigning for a laptop for every teacher. The NASUWT has now called on ministers to introduce a national training strategy for ICT.
The scheme to provide computers has been suspended but will continue next year.