A mother whose two children died of carbon monoxide poisoning in a Greek hotel said she was "shocked" at a damages payout to the tour operator.
Robert Shepherd, six, and Christianne, seven, of Horbury, West Yorkshire, died at an apartment in Corfu in October 2006.
Tour operator Thomas Cook was cleared of responsibility at a trial in Greece in 2010.
The firm was awarded damages against the hotel's owner.
The High Court hearing related to costs incurred by the tour operator after two of its employees were tried, and cleared, by a Greek court of negligent manslaughter in 2010.
Thomas Cook confirmed it had been awarded an interim payment of £1m by the court.
The two children were overcome by fumes from a faulty gas boiler while on holiday at the Louis Corcyra Beach Hotel in Gouvia, with their father Neil Shepherd and his partner Ruth Beatson in 2006.
Mr Shepherd and Ms Beatson were both left in a coma as a result of the accident, but survived.
The manager of the hotel and two other members of staff were convicted of manslaughter.
The hotel owner has paid damages to the children's parents.
The children's mother Sharon Wood said that she had not been told that Thomas Cook was taking legal action against the hotel owner.
In a statement, she and her husband Paul said: "We were very shocked to hear that Thomas Cook have been successful in claiming damages relating to the deaths of our children.
"It's been a huge financial burden attending the six-year judicial process in Greece, on top of the life-long pain of losing Christi and Bobby.
"We reluctantly took a settlement last year from the hotel group which amounted to far less than the interim payment which Thomas Cook has received.
"We accepted the offer due to the state of the Greek economy and we believe had Thomas Cook kept us informed of their high court appeal a more appropriate settlement would have been achieved."
A spokesperson for Thomas Cook UK and Ireland said: " What happened in Corfu was a tragedy, and the thoughts and sympathy of everyone at Thomas Cook will always be with the family and friends of Christianne and Robert Shepherd."