Morrison won't give unions advice on wages

Treasurer Scott Morrison insists the wage growth projections in his budget are conservative but says workers can't just assume better days are ahead.

The budget predicts wage growth will reach 3.75 per cent by 2020/21, almost double the rate now and was seen as one of Treasury's more optimistic forecasts by economists.

Asked on ABC television on Sunday whether unions should lock in that figure in wage negotiations, Mr Morrison said: "I'm not going to give unions any advice, I doubt they would take it from me."

"My advice to companies is to grow, become more productive, take the opportunities you have got out there and when you have the opportunity because of increased profitability to share that with your employees. I believe they will."

He said neither workers nor business could assume better days are ahead.

"They have to be secured. We have to achieve the growth in order to achieve these results."

He explained the wage growth projections were based on the downturn in mining investment having run its course and the terms of trade starting to improve by the end of the four-year budget estimates.