Westpac has opened its branch network to anyone who wants to search for lost superannuation accounts.

"Westpac is quite serious about doing something about [lost super] today. That is why we've put the whole Westpac network behind the Australian lost superannuation service," Westpac retail and business banking group executive Rob Coombe said yesterday.

"All of our people throughout 700 branches in Australia are instructed to get out and help our customers, or indeed anyone, who has lost super to help them track it down and to assist them in consolidating their super."

Westpac released a study that estimated 5.8 million working Australians could be missing up to $18.8 billion in superannuation savings.

"The government is congratulating Westpac in reuniting people with their lost super," Financial Services and Superannuation Minister Bill Shorten said.

"You wouldn't leave $100 on the ground, but that is what happens with lost super."

Shorten said workers should not worry that their lost super would be eaten up by fees.

"If no money goes into an account for two years, the account gets transferred to a free government account. The money is there, you just have to chase it up," he said.

He said the initiative was launched yesterday because the super system had matured to such a degree that lost super was now becoming a real problem.

"Super is now 20 years old; 10 years ago it wasn't such a problem," he said.