ETS has lost pound;50 million this year because of the marking fiasco. And the company told a Parliamentary committee it does not know when this year's marking will be finished.
The tests this summer were the first of ETS's original five-year contract, which has since been terminated at a cost to it of pound;19.5 million.
ETS said it decided to pull out of the Sats marking contract in June. Philip Tabbiner, director of ETS's supervisory board, said: "We are not in the business of absorbing pound;50m losses."
He said the National Assessment Agency "shared significant responsibility" because it had changed the system for training markers two months before.