Irish speakers picketed all-party talks on equality and human rights at Stormont yesterday claiming their rights had been ignored.
The budget of Foras na Gaeilge, the cross-border body with responsibility for the language, was recently slashed by more than £2 million.
"It is one of the most striking examples of the failure to implement the agreement which established the body in the first place," Janet Muller of Pobal said.
"It is little wonder that the Irish-speaking community sees the cuts as an attack on the peace process and the central role of the Irish language in the building of a new society."
The cuts have come at a time when the census has reflected the growth of the Irish-speaking community. More than 10% of the population of Northern Ireland now claims to have a knowledge of the language.
Protestors warned that even without such cuts, the budget had already run out of funds last April.
"We are calling for an immediate review of the cuts. These funds are ess-ential for various types of development work, buildings, children's programmes and arts programmes," Ms Muller said.
A "slow, bureaucratic process" had also led to delays in the development of Foras na Gaeilge's office in Belfast, she added.
"After three years, the office has not been properly staffed and is not fully functional," she said.
Tommy Gallagher, SDLP spokesman for education, said there was "grave disquiet among people who were trying to promote Irish language and culture".
"The lack of the TG4 coverage which was promised in the terms of the Good Friday Agreement is unacceptable," he said.
"Coverage for the Irish-speaking television station is available in only 50% of Northern Ireland. It is worth noting that Scots can avail of £12.5 million to promote their language."
Sinn Féin Irish language spokesman Barry McElduff said: "The agreement signalled a different approach to Irish language rights, we now need to see the political will of the British government fully implement the agreement in the area of language rights and a reversal of the cuts in support for Foras, as well as a fund to finance Irish language programming."
