David Bowen revealed that the Cambridge and Huntingdon Health Commission was paying pounds 200-a-month towards the costs of his daughter's treatment.
But he said that he needed a minimum of pounds 400-a-month to ensure that Jaymee received the best treatment.
Mr Bowen, 32, was speaking outside the Portland Hospital in central London, where Jaymee is spending her half-term while her drug regime is adjusted.
Her case was highlighted after the decision was taken in the spring not to give Jaymee more major treatment on the NHS.
Mr Bowen began his fight in the courts for continuation of aggressive cancer treatment on the NHS, but he failed to secure it.
An anonymous benefactor provided pounds 65,000 for Jaymee to be treated at a private clinic where she underwent an experimental transfusion using white blood cells from her sister.
Dr Peter Gravett, the consultant haematologist who has been treating Jaymee, has said that following treatment her chances are now 20 to 30 per cent of remission, or "possibly a cure".
But Mr Bowen said that Jaymee needed to visit the Portland Hospital at least twice a month, and there were the costs of drugs and any other treatment to be met.
Mr Bowen said that while the Portland Hospital was not currently pressing for fees, the cost of treatment had resulted in debts of more than pounds 2,500 since September.
He said it had not been decided exactly who was going to be sued, but it would include those people who treated her under the NHS.
"It's going to be on the grounds that we feel there are very serious questions to be answered and a lot of niggly points about how she was treated," said Mr Bowen.
He said his solicitors were currently looking at who was responsible for Jaymee's treatment under the NHS. He said the health authority had had its chance to treat her, but had "blown it".
The money from the anonymous benefactor had now dried up, he added. Jaymee was suing in her own name and therefore qualified for legal aid.
"This is the most difficult time in my entire life. I really hope I will never have to go through with it again. But if I have to I will," he said.
Later, Jaymee went out shopping with her nine-year-old sister, Charlotte.
Wearing a yellow sweater and black leggings, she looked downcast and tired outside the hospital. She said: "I want to buy some shoes."Reuse content