Ireland's voting power in Europe could be cut to a third of its present level.
Euro sceptics The People's Movement are warning that a new weighting system for votes could see our influence on the European Council reduced to 0.8%.
It also claims the changes, due to begin next month, will allow Germany, France, Britain and Italy to hold almost half the voting power.
Protesters will mount a picket outside the Dáil this lunchtime to voice their anger over the new rules.
Kevin Mc Corry of The People's Movement said: "The six largest EU states will increase their combined voting from 49% to over 70% while the smallest states will fall from 51% to less than 30%," he said.