The German defence ­ministry has no overview of the costs it is incurring for Airbus Group's Eurofighter jets and will spend twice as much as it originally planned on the country's most expensive defence project, federal auditors said.

The German Federal Court of Auditors, which oversees the government's financial management, said in a report the costs for the Eurofighter jets over their life-cycle would climb to about €60 billion ($83bn) from an originally planned €30bn, despite a reduction in the number of jets.

The auditors said ­operating expenses, ­especially maintenance costs, had increased particularly strongly.

They also said the budget of €11.8bn that the defence ministry had calculated in 1997 for the purchase of 180 Eurofighter jets would be enough to buy only 140 of the planes.

A spokesman for the defence ministry said at a government news ­conference that it was ­important to distinguish between costs that had already been incurred and future costs.