The global conference on climate change is being chaired by Fiji's Prime Minister Frank Bainimarama, but Tonga's delegation will not include a cabinet minister.
Siaosi Sovaleni headed the ministry responsible for the environment and climate change until he was sacked days after Parliament was dissolved in August.
The election was subsequently brought forward a year to next week.
Mr Sovaleni said an unfortunate by-product is the lack of ministerial presence at COP 23.
"I do believe that Tonga is a small country [but] it should have some contribution towards this global problem that we have. It's unfortunate that, because of timing, that we can't be represented at that level so that we can see how we can contribute to this global problem but also to see how we can actually try and mitigate the potential problem to Tonga."
Photo: RNZI/ Koro Vaka'uta Siaosi Sovaleni