Reform UK's Deputy Chair on Cornwall Council has quit the party over views he says "diverged from those of the party".
Councillor Rowland O'Connor will not sit as an independent after making the decision.
The councillor who represents St Mawgan and St Wenn said his views and priorities on how to serve local residents have "increasingly diverged from those of the party".
In a message to residents, he said: "I would like to share an important update with you personally".
"After careful reflection, I have decided to resign from both the Reform UK party and my position as deputy chair of the Reform UK Council Group within Cornwall Council," Mr O'Connor added.
“This decision was not taken lightly."
He said that it became clear "over recent months" that his own views and priorities "for how best to serve local residents have increasingly diverged from those of the party".
"To continue representing our community with honesty and independence, I believe it is right to step away from party affiliation," Mr O'Connor added.
Rowland O'Connor will now be an independent
|“I want to reassure residents that I will continue to serve as your Independent Cornwall councillor for St Columb Major, St Mawgan and St Wenn.
"My focus remains the same, listening to your concerns, standing up for local people, and ensuring our voice is heard at Cornwall Council."
Mr O'Connor added that it was "an hour to represent you and to work alongside so many dedicated councillors, parish representatives, and officers who share a deep commitment to our area".
"I will continue to work constructively across the Council and with our communities to deliver improvements in transport, local services, and affordable housing," he said.
The councillor will stay on at Cornwall Council
| WIKIMEDIA COMMONSLATEST DEVELOPMENTS
"I remain available to all residents for casework and support.”
Liberal Democrat MP Ben Maguire welcomed Mr O'Connor's decision, saying the constituency was now "Tory and Reform free".
"People across North Cornwall are turning away from populism and political point-scoring, and towards real, practical progress," he said.
"I look forward to continue working with Cllr O'Connor and other Lib Dem and Independent councillors in North Cornwall.
"For the good of all our residents and I've already been able to support them with a number of big wins."