Tonga's tripartite committee, established by Parliament in July to consider political reform, has collapsed.
The committee was made up of nine parliamentarians and was due to report back on Thursday this week, after being given an additional month to resolve issues.
But our correspondent in Tonga, Mateni Tapueluelu, says there were two key matters on which they could not agree.
"They can't agree on the constituency issue and the timing for political reform. And therefore they have agreed to go back to Parliament and the agenda of political reform will have to be decided by Parliament collectively."
The pro-democracy MPs wanted the reforms in place by next year but the Government says more time is needed, while the Government wants MPs to be elected by districts rather than island wide as is now the case.