About 400 Centrelink customer service centres around the country are bracing for chaos on Monday morning after the national welfare agency unilaterally changed its opening time from 8am to 8.30am without informing clients.

The move, which the Community and Public Sector Union calls a deliberate tactic to stall current enterprise bargaining negotiations, was announced to some staff via email yesterday. But there was no consultation with welfare recipients, with customer service advisers frantically phoning clients this morning to alter appointment times.