Labour's finance spokeswoman, Ms Joan Burton, claimed the Government was continuing to create new tax loopholes and benefits for the rich while starving health and education services of cash.
During a debate on economic policy, delegates made sharp criticisms of the Coalition, claiming it had broken election promises and was knowingly creating a deeply divided society.
Ms Burton maintained: "For all his bluster about closing tax loopholes this Minister is just as busy creating new ones and ignoring some very notorious existing ones."
She said the tax exemption for stallion fees was just the headline example.
She said a consortium who got a franchise to charge motorway tolls got capital allowances against tax as well as a 65 per cent direct subsidy for constructing the road.
"A triple whammy for the road-user who pays the subsidy, pays the tolls and now offers a tax break to the promoters. A triple licence to print money from FF," said Ms Burton.
"A group of rich medical professionals can buy an office building and lease it back to the tenants.
"They get long-term allowances to eliminate their tax bills over a very long time-scale. Huge incomes, no tax."
The conference adopted a motion calling on the party to outline a detailed policy on taxation within the next 12 years following consultation with the membership.
The conference unanimously approved a motion condemning recent restrictions to the freedom of Information Act and committing Labour "to upholding and extending the principle of freedom of information".