Ontario's auditor general says it may be the most expensive fare-card system in the world, but the Presto smart card system is not going away.

Already in use in a few areas, Presto is supposed to be a convenient way of moving seamlessly from one transit system to another.

Originally it was supposed to cost $250 million. But in Wednesday's report auditor general Jim McCarter said that will balloon to more than $700 million in development fees.

Toronto-area transit riders will be able to use the PRESTO fare card in all subway stations, buses and streetcars by 2016. (Metrolinx)

Much of the extra cost comes from Presto's Next Generation System, allowing users to pay with credit, debit cards even cellphones.

But in response to the auditor's report, Metrolinx CEO Bruce McCuaig says his organization will do more of the work on Presto itself and rely less on the contractor Accenture.

"This is all about continuous improvement for us and we recognize that we can always get better," said McCuaig.

The auditor general was critical that only 18 per cent of transit users have a Presto card, but with the TTC recently signing on McCuaig says that will change

"Over the next couple of years — and especially when the TTC is fully on board — we're going to see the system grow to about 2.5 million customers," he said.

McCuaig also points out that Metrolinx now owns the rights to Presto in Canada and will get royalties if Presto is sold anywhere else in the world.