They came, they spoke, and they left on private jets. But the hangover for the taxpayer from last year's G20 leader's summit in Brisbane goes on.

A dozen hotel bills and taxi fares for G20 attendees have been upwardly revised by $1.8 million in recent months, government tender documents show.

A single contract with Cabcharge for the provision of taxis was originally $50,000 but payment to the company has since risen to $627,000 – an increase of more than 1200 per cent.

In total,12 contracts with hotels and serviced apartment providers blew out from $917,000 to $2.2 million.