Some Dutch politicians have argued for a writedown of ordinary bonds of troubled Dutch banking and insurance group SNS Reaal, the paper said.
SNS Reaal, which received Dutch state aid in 2008, is widely expected to require a second bailout because of problems at its property unit and is due to come up with a restructuring plan when it reports its earnings next month.
Fitch could not immediately comment.
"We say now that the chance is 99.5 percent that the government supports ordinary bond holders. If this assumption proves to be wrong you should no longer look at banks' current rating but at their viability rating," Gandy was quoted as saying, without specifically referring to SNS Reaal.
A viability rating, which indicates a credit judgment without implicit state guarantees, is usually two notches lower for big banks than current ratings, the paper said.