Ben Houchen, the mayor of Tees Valley, said the former prime minister should have “more awareness” than to be in Manchester.
Rishi Sunak’s attempt to set out his vision for the county is at risk of being overshadowed by Tory in-fighting.
Truss is due to hold a rally of supporters tomorrow on the fringes of the conference in which she will demand Sunak cut taxes.
The high-profile intervention has been seen as part of positioning for the next leadership contest should the Conservatives lose the general election as currently expected.
Speaking at a conference event hosted by the conservative Onward think-tank, Houchen hit out at Truss for even turning up in the city.
“I thought Liz Truss would have more awareness than to, for example, come to Conservative Party conference,” he said. “I don’t think she should be here.”
“If you look last year Rishi didn’t come. Because she was the prime minister. I think he did the right, grown up, sensible thing
Houchen added: “I am disappointed to see Liz has chosen to take a different path.”
He also said while the Conservatives could win the election, he would not bet on it “at the moment”.
The Tory peer wared “time is running out” for Sunak to convince voters to back him.
Taxes are currently at their highest level since WWII and Sunak is under pressure from Tory MPs to cut them before going to the polls.
Speaking to BBC’s Sunday with Laura Kuenssberg programme, the prime minister said he wanted to reduce taxes but would not say when.
It came after Michael Gove, the levelling up secretary, had earlier told Sky News he did want to see tax cuts soon.