Wiktionary
trades unions
n. 1 (trades union English) 2 (trade union English) ''when referring to unions representing different trades.''
Usage examples of "trades unions".
But I'd need him back for the opening of Parliament--especially if your hunch turns out to be right and Menzies does announce a bill to curb the powers of the trades unions.
There were four long mimeographed statements from four trades unions, setting forth extremely complex grievances which the Government was admonished to settle at once.