Both SIPTU and Mandate are seeking talks after the DAA introduced the policy without consulting the unions. The company informed them of the move in a letter sent to them by the DAA's senior employee relations manager John McCormack.

Relations between the unions and the airport's management have deteriorated rapidly over recent months and the DAA's approach towards ongoing pension talks has also angered the unions, according to correspondence seen by the Sunday Tribune. In one letter last week, SIPTU accused the DAA of "blatant obstructionism" and engaging in "disingenuous requests for information they already have".

In the letter, McCormack stated that the DAA had decided to introduce the ban until it was clear whether it had won the contract to operate the airport's second terminal.

Although the DAA is currently building the terminal, the contract to run it has to be put to tender, under the deal reached within the government over the Progressive Democrats' support for the terminal.

A DAA spokesman said that if the DAA did not win the contract, it might not require some of the staff it hires between now and the second terminal's opening "because a proportion of overall airport passenger numbers will be processed by the staff of another operating company".

He insisted that the company had consulted the unions about the ban. "The latest document agreed by the company and the trade unions, relating to passenger security staff, has this clause incorporated in it."

He added that, on the pensions issue, the company planned to have discussions with the unions in June.

However, SIPTU's aviation branch organiser Dermot O'Loughlin said that his union had not been consulted about the changes. He said that the DAA was presenting the contents of security staff deal out of context.

"Instead of discussions, all we get are very hostile, robust letters which create a negative environment, " he said.

O'Loughlin said that the changes could have passenger safety implications, especially if the DAA recruited emergency service workers such as airport police officers and fire fighters on a temporary basis.

He confirmed that SIPTU had called an emergency meeting for its airport shop stewards to discuss the ban and several other industrial relations issues. He refused to comment, however, on the contents of recent correspondence between the DAA and the union.