The Democratic Party Wednesday turned new controversy over an Air Force tanker deal into a searing election attack on Republican White House hopeful John McCain.

The Democratic National Committee, which is now fused with Barack Obama's presidential campaign, accused the Arizona senator of weighing in "on behalf of his lobbyist friends" to steer the tanker deal to European giant EADS.

A congressional audit by the Government Accountability Office backed Boeing's protest over the award of the huge mid-air refueling contract to Northrop Grumman and EADS, and recommended the Air Force review the deal.

"Now that the GAO has found that the tanker deal was not the 'open' and 'transparent' process he claimed to be seeking, Senator McCain has a responsibility to stand up for America's working families and insist the Air Force reopen the bidding on this tanker," DNC spokeswoman Karen Finney said.

"After siding with his lobbyist friends in helping steer tens of thousands of manufacturing jobs overseas the last time around, Senator McCain has an opportunity to do the right thing now," she said.

"Given his history of promoting policies that outsource American jobs, we're not holding our breath."

At least three top advisers to McCain's White House campaign reportedly took part in lobbying activity on behalf of the European Aeronautic Defence and Space Company (EADS), parent of Boeing's arch-rival Airbus.

Boeing lost the 35-billion-dollar contract Air Force contract for 179 tankers in February, and complained bitterly that the Pentagon process had been unfairly tilted towards Northrop Grumman and EADS.

The US aviation giant was first awarded the contract in 2003, but a Senate investigation led by McCain exposed a procurement fraud scandal at Boeing and the bidding was reopened.

There was no immediate comment from the Republican's campaign.