Irish atheists and secularists have accused their government of breaking a promise to call a referendum over the Republic’s controversial blasphemy laws in the lifetime of the current coalition.

Atheist Ireland expressed disappointment that the government had quietly dropped plans for a plebiscite to rid the country of the legislation, which secularists have argued are incompatible with modern Ireland.

Last year, the Fine Gael-Labour coalition had promised a referendum on the blasphemy law to coincide with two other votes on gay marriage equality and lowering the age for when a citizen can become president of the state.

Earlier this month, however, the government confirmed that referenda will be held in the spring on gay marriage and the age of a presidential candidate, but excluded a national vote on blasphemy.

Michael Nugent, a co-founder of Atheist Ireland and a Dublin-based comedy writer, said: “If they refuse to hold it at all during the term of office of the government – as an unnamed government spokesperson hinted at earlier in December – then yes that is a betrayal.’

Nugent pointed out that both ruling parties pledged before the 2011 general election to reform the blasphemy law with Labour explicitly vowing to take the word out of the Irish constitution.

He said the back-tracking on the issue would “continue to undermine confidence in the constitution and the legislature. It will continue the ‘nod and wink’ politics of the recent past, where we are expected to believe that (politicians’) words do not mean what they say, and to not take seriously what is in our constitution.”

The author of a comic opera co-written with Father Ted writer Arthur Matthews added: “Ireland’s blasphemy law will continue to give encouragement to Islamic states at the UN, as they point to a modern western democracy passing a new blasphemy law in the 21st century when defending their own blasphemy and apostasy laws.”

The Republic’s blasphemy law was only introduced in July 2009 by the then Fianna Fáil-led government. Breach of the law is punishable with a fine of up to €25,000.

The law defines blasphemy as “publishing or uttering matter that is grossly abusive or insulting in relation to matters sacred by any religion, thereby intentionally causing outrage among a substantial number of adherents of that religion, with some defences permitted”.

The former Fianna Fáil justice minister Dermot Ahern has defended the law, claiming it is necessary because the 1936 Irish constitution extends the protection of belief only to Christians.