Maids would face a benchmark test on completion of two weeks' training by the Employees' Retraining board, under a new proposal.
But Lee Cheuk-yan of the Confederation of Trade Unions said most labour representatives on the board had opposed the idea when it was floated by the secretariat on Tuesday.
He understood the Government was exploring the idea of introducing similar centralised tests for different trades.
Maids currently face a two-week standardised training period funded by the board and will face an internal test on completing the training. Each year, there are 10,000 places on the course.
Mr Lee said introducing a benchmark test would mean workers would face two tests - an internal one and the centralised benchmark test.
Those who pass both will be awarded a card to allow them to register with the Labour Department, which will list their names on the Internet for prospective employers.