More than 170 people have signed an online petition against plans for an unitary authority in Cornwall.
The petition features on Downing Street's website.
It asks the prime minister to reject the bid and to replace the county council with a Cornish Assembly of democratically elected members.
The council said a single authority would save money, but six district councils, which would be scrapped if the bid is approved, dispute this.
Cornwall is among 16 short-listed to become a unitary authority.
A final decision will be made by the government later in the summer.