The move is likely to further anger the company's unions, which have unsuccessfully attempted in recent weeks to secure a guarantee from the Minister for Natural Resources, Noel Dempsey, that the technicians' jobs are safe. But a spokeswoman for Dempsey's department has defended the potential use of outside contractors.

"The engagement by the ESB of external contractors to assist with the rollout of its major grid upgrading programme is recognised to have significantly helped in accelerating progress on the programme, " she said.

Sources have said the maintenance of the network will definitely be outsourced as Eirgrid has no interest in setting up its own maintenance operation. The network management company's preferred option is understood to be to award a long-term maintenance contract to the ESB.

However, sources said that no possibility could be ruled out at this stage, particularly as Eirgrid and the ESB have yet to open negotiations on the asset transfer.

Brendan Ogle, the ATGWU's regional organiser for the ESB, said any form of outsourcing would be opposed by the unions.

"It would generate additional costs for the consumer as there would be a contracting fee between Eirgrid and the ESB which would have to be recovered. To date, all such costs have been passed on to the consumer, " he said.

Ogle said if the contract was awarded to a firm other than the ESB, it would lead to more conflict between the government and the company's staff.

"If outsourcing is what the minister wants, he is going to bring us all back into dangerous territory, " he said.