Cllr Dominic Fosker, a Liberal Democrat who represents Logan Ward in Market Harborough, moved away to Farnham in April to take up a new job and be nearer his family.
But Cllr King, who heads up Harborough District Council, said: “Cllr Fosker should step down now.
“His position on our council has become entirely untenable.
“He should do the decent thing, examine his conscience and resign now.
“How can he go into battle for his constituents in Logan ward when he lives well over 100 miles away?
“He can’t,” Cllr King told the Harborough Mail.
“Cllr Fosker might be legally able to move away and still sit on the council.
“But morally and ethically this is just wrong.
“He can’t represent the people on his ward in Market Harborough, it’s as simple as that.
“He didn’t attend the full council meeting on Monday night.
“Our councillors can claim a basic allowance of £5,669.61 a year,” said the Conservative authority boss.
“Yet we’ve only got three meetings left this year that he can turn up at.
“I get sick and fed-up of being lectured by the Opposition leader (Phil Knowles) about what’s right and what’s not.
“But I haven’t heard a word out of him over this.
“It’s double standards – it’s a joke and we should have a by-election.
“If Cllr Fosker was one of my group then he’d have to go.”
Elected in May 2019, Cllr Fosker told us: “I intend to serve out my full term as councillor for Logan ward until the elections next May.
“I’ve taken advice from our officers and I have every right to stay on as councillor because I have business interests in Market Harborough.
“I am saving the council the cost of staging a by-election.
“As for my councillor allowances, I am talking to our officers about trying to get that money paid straight to a local charity,” said the dad-of-one.
“I want to keep that cash in Market Harborough.
“I’ve loved serving the people of Logan ward for the last three years.
“And I am continuing to do my best for them.
“I’m in touch with them digitally all the time by email and online.
“I also work very closely with my councillor colleague, Barbara Johnson – we’re a good team,” said Cllr Fosker, an automotive engineer who moved to Market Harborough in 2014.
“I’ve become a father since becoming a councillor and I’ve moved to be nearer our families.
“And residents have been very supportive.”
Cllr Phil Knowles, who leads the Liberal Democrats on Harborough council, said: “Cllr Fosker has checked with our officers and made sure that he’s OK legally to do this.
“This is just an opportunity for Cllr King to make the comments that he is making.
“I cannot tell anyone to resign or not to resign.”