MEPs are pushing for "protected envelopes" for the Common Agricultural Policy (CAP) and cohesion.
MEP Nina Carberry warned that the European Parliament could move to block part of the EU budget as soon as next week, unless the European Commission rewrites proposals that seek to merge agriculture and regional funding streams.
The warning comes after EU Budget Commissioner, Piotr Serafin faced sharp questions from MEPs this week over the proposals.
European Parliament party leaders have written to the President of the European Commission, Ursula von der Leyen in recent days to declare their opposition to the next EU budget proposals.
Speaking after the hearing, MEP Carberry - Ireland's only member of the European Parliament's Budget Committee - said the parliament supports simplifying the budget and making it easier to draw down on funds, particularly in agriculture.
"But, there is a lot of frustration with the National and Regional Partnership Plans (NRPP), which merge cohesion and agriculture funding," she said.
"We need protected envelopes for CAP and cohesion, and stronger guarantees for parliamentary oversight as to how the money is spent."
The Fine Gael MEP said that the commission's attempts to streamline funding are "well intentioned - but flawed".
She pointed to the range of challenges farming faces today, from generational renewal to cost pressures across the board.
The European Parliament must give its consent to the long-term EU budget, which finances all EU flagship policies before it can come into force.
The Department of Agriculture, Food and the Marine (DAFM) heard concerns about the post-2027 this week from TDs and senators this week.
Paul Savage, assistant secretary general at the DAFM, said that at this stage, funding announced for CAP is "a proposal, it's the start of a long process".
He was speaking at a meeting of the Oireachtas Joint Committee on Agriculture and Food.
The reduction in ring-fenced CAP funding presents challenges for Ireland, Savage said.
However, additional CAP funding can potentially be drawn from the broader NRPP envelope allocated to each member state.
"There is scope to move additional funds from that wider NRPP allocation into the CAP for member states," Savage explained.
"We have to look at that and see how is that going to work, how will that fit with the broader targets that are there for the NRPP in terms of social cohesion and other things required."