text: The contractor, Smartty's Management Limited, has been asked to return the excess payment, the government said.
  On Wednesday, Transport Minister Dzifa Attivor resigned following a public outcry over the deal.
  Ghana is struggling with a large budget deficit and a widening public debt.
  The branding involved respraying the 116 imported passenger buses and adding portraits of the current President John Mahama, his three immediate predecessors and Ghana's first head of state, Kwame Nkrumah.
  A proper procurement method was "not followed and the contract did not ensure value for money," the government said after a review by Attorney General Marietta Brew Appiah-Opong.
  Opposition and anti-corruption campaigners have raised concerns over the amount spent, which they said was far too much, forcing the presidency to set up an investigation.
  The BBC's Sammy Darko in the capital, Accra, says many people think the government is not doing enough to tackle budget mismanagement.
  They want to see people being charged for causing financial loss to the state, he adds.
  Mrs Attivor's resignation is the first by a Ghanaian minister in more than a decade and comes amid efforts by the government to cut spending as it implements a three-year International Monetary Fund plan to restore fiscal stability.
  Earlier this week, Mr Mahama banned public officials, including ministers, from first class air travel and he suspended non-essential trips.
target: Ghana has demanded a $500,000 (£350,000) refund after its transport ministry spent $1m to paint more than 100 buses with portraits of the country's recent leaders.