BHP chief executive Andrew Mackenzie says overworking is unhelpful.

Mr Mackenzie has spoken about the importance of working less in an interview with the Qantas inflight magazine.

“A rested Andrew can do more in four hours than a tired Andrew can do in eight,” he said.

“It's not only diminishing returns; [not being rested] is like a scorpion's tail — it can undo things.

“That's true of everyone's productivity and particularly in an intellectual role like that of a CEO.

“A lot of boards don't get that. People need to be fresh.”

A lot of workers pride themselves on putting in ludicrous hours, being the first into the carpark in the morning and the last to leave, because they think it will impress their bosses.

But Mr Mackenzie said in an increasing global business environment – where workers are often talking to colleagues in other countries late into the night or early in the morning - it is nonsense expect much of them during normal office hours.

“If people have a lot to do late at night or early in the morning there needs to be some compensation for that or they're going to suffer from the scorpion's tail of performance,” he said.

“I get into the office quite late by modern standards and I leave quite early because I know I am going to be working in the evening.”

Mr Mackenzie says that as with many things, quality of work trumps quantity.

“You don't have to be the smartest person in the room to be a CEO, but you do need to be sharp,” he said.