The Teessiders' latest accounts show the club made a loss of £13.93million during the year ending June 2013, meaning Gibson and his ownership group are having to plough in more than £1million a month to support it.
However, chief executive Neil Bausor insists Boro are in a healthy position despite the drop in revenue they have suffered since relegation from the top flight in 2009.
He said: "Middlesbrough Football Club continues to hold the enviable position of being a club without any external debt and with a very stable ownership.
"Steve Gibson and the group continue to be fully committed to support our ambition to return to the Premier League.
"Balancing our ambition for the first team against a challenging environment of Financial Fair Play rules is not easy, but we remain determined to use our financial resources to the maximum effect."