Fine Gael Galway senator Fidelma Healy Eames said where farmers are concerned, the 1% levy should be calculated from net and not gross income. This was because farmers were forced to pay big overheads from gross earnings before a net income was realised.
"There is a strong case to be made for legally testing the calculation of the one per cent income levy for farmers in this way because, quite simply, farming is a business.
"Gross income is not the same as net income and all costs have to come out of gross income for the farmer before net income or profit is realised," Healy Eames said.
These costs included feeding, fertiliser, diesel and veterinary charges. Some farmers were seeing feeding costs alone of up to EUR500 (£452) a day.
"It is only after these costs are deducted that the farmer takes in any profit - just like any normal business," he said.
Healy Eames, who was speaking on pre-budget statements, said average part-time income in farming was currently EUR16,000 (£14,460) and full-time income around EUR20,000 (£18,073).