Melbourne myki top-up leaves woman $2.7m debt

A Melbourne woman topped up her myki card only to find the ticketing system thinks she owes almost $2.7 million.

Sarah Coles posted a photo of her myki receipt on Twitter after putting $5 on the card.

"Myki reckons I owe them $2,684,350. I think this might be incorrect," Ms Coles posted on Thursday.

The myki public transport card system was criticised in an Auditor-General's report on Wednesday, after eight years and $1.5 billion spent on it.

Auditor-General John Doyle blamed weaknesses in the original contract signed in 2007 for cost blowouts and poor monitoring.

"The overly ambitious and vaguely specified initial project scope and contract for myki contributed to this outcome," Mr Doyle's report said.

Public Transport Victoria also paid out more than $1.4 million in performance incentives, despite having no way to know if operator NTT Data's reported results are correct.