Labour says it has proof of ministerial interference in Auckland's $110 million public transport ticketing scheme, and the Government should cover ratepayers for any extra costs.
Labour transport spokesman Phil Twyford says correspondence between Wellington smart-card supplier Snapper and the Beehive shows the Government forced the former Auckland Regional Transport Authority to let the company join the Hop ticketing scheme after awarding the main contract to its rival, Thales.
Auckland Transport has since dumped Snapper for allegedly missing performance deadlines, a claim which the company denies.
Mr Twyford says Government denials of political interference are contradicted by a letter from Snapper chief executive Miki Szikszai to former Transport Minister Steven Joyce after a meeting in 2010.
Mr Szikszai wrote that he understood Mr Joyce's "expectations are that ... NZ Bus should be free ... to implement Snapper equipment and join the Snapper scheme in Auckland."
NZ Bus and Snapper are both owned by Infratil.
The company decided late in 2009 to equip its 650-strong Auckland fleet with Snapper machines, but Transport Agency and Auckland Transport opposed that as posing risks to its integrated scheme for buses, trains and ferries.
Mr Twyford said the letter showed Transport Minister Gerry Brownlee was wrong when he assured Parliament in June that there had been no political interference.