Irish rights activists have accused the Northern Ireland Secretary of ignoring repeated requests for a meeting.
The An Dream Dearg campaign, which is lobbying for the introduction of an Irish language act in the region, accused James Brokenshire of an "inexcusable dereliction of duty".
An impasse over the language issue is preventing the restoration of powersharing at Stormont.
Sinn Fein will not go back into government with the Democratic Unionists without one.
The DUP, for its part, will countenance a broader culture act, that incorporates the Ulster Scots culture, but will not accede to a piece of legislation that only offers protections to the Irish language speaking community.
Mr Brokenshire's efforts to foster an agreement between the two sides have so far failed to deliver any results, with the prospect of Westminster direct rule at Stormont now looming large.
An Dream Dearg penned an open letter to the Conservative MP criticising his handling of the matter.
The campaigners insist the UK government committed to the introduction of an Irish Language Act in the 2006 St Andrews' Agreement.
"Despite our best efforts to secure a meeting with you, including contacting your office on numerous occasions and over 50 children personally handing over letters at your residence asking for a meeting, we have yet to hear from you," they wrote.
"This is an inexcusable dereliction of duty given the prominence of the question of rights for Irish speakers in the ongoing political crisis.
"Almost 11 years ago, the British Government made a clear commitment in an international agreement to introduce an Irish Language Act.
"Failure to do this has led to consistent condemnation from the United Nations and the Council of Europe; has obstructed the development of the Irish language; and made it a subject of attack and point-scoring at the assembly."
They said there was "nothing strange, wrong or excessive" with the call for legislation to protect and enhance Irish.
"In Wales, for over 50 years, Scotland and in the south of Ireland legislation has been developed to achieve just that," they added.
"It must be stressed that that legislation to protect their native languages has not heralded any crisis or decline in either health or education provision.
"This is clear not here, but across the world.
"Given your role as the representative of the British Government and that Governments clear commitment to our community, it is not acceptable for you to remain 'neutral' or 'objective' on this key issue.
"To ensure concrete expression is given to promises made by your government, you must actively pursue and encourage the adaption and implementation of an Irish language Act; to provide the same equality to the Irish-language community that has been afforded to other native languages in other jurisdictions; to use their power to ensure rights, respect and recognition in our society.
"A minority opposes change; a majority calls for an Irish language Act.
"It is time to practice what has been preached, and in your role as representative of the British Government, to finally fulfil a promise that was made."
A UK Government spokeswoman said the letter had been received and "will be considered".