Rio denied appeal on worker agreement

Rio Tinto has not been allowed to appeal against a court's decision to declare an employment agreement for its Pilbara iron ore workforce invalid.

But the miner says pay and conditions will not change for employees previously covered by the agreement.

The High Court on Friday rejected Rio Tinto's application to appeal against a previous decision of the Federal Court, which found that an employment deal covering workers at its iron ore mines in the WA region was not a genuine collective agreement.

The Construction, Forestry, Mining and Energy Union started the legal action in 2009 after Rio Tinto signed up workers on Work Choices individual contracts to a binding five-year non-union agreement before the Fair Work Act became law.

The Federal Court and High Court upheld the union's argument that the agreement - negotiated with a small number of workers - was not reached through genuine collective bargaining and should never have been ratified.

"The employees are now agreement-free and are able, should they wish ... to genuinely collectively bargain with their employer," CFMEU mining general secretary Andrew Vickers said in a statement.

In a note to employees, Rio Tinto said the invalidation of the agreement would have no impact on pay and conditions of employees covered by it.

"We will continue to monitor terms and conditions for all employees to ensure they remain rewarding, attractive, fair and competitive, and will make changes where necessary and appropriate to ensure they do," the note said.