Former federal MP Craig Thomson's request to pay his $25,000 fine for theft in $50 instalments has been denied by the Victorian County Court.

Following a protracted court case and appeal last year, Thomson was found guilty of theft against the Health Services Union during his time as national secretary and was handed the fine.

Thomson told Judge Lisa Hanna on Friday his income was less than $3,000 a month, and requested paying off the fine in $50 monthly instalments until things improved.

Ms Hanna said to allow the suggested payment plan for such a large fine would be "simply unacceptable".

Under the suggestion, it would take 41 years to pay off the whole fine if Thomson's financial situation did not improve.

Ms Hanna reminded Thomson the fine was the only thing standing between him and days in jail.

She asked him to return to court in a month with a more viable payment plan.

Thomson refused to talk to media outside court.