David Cameron was mistaken over his claim to be life patron of a beekeeping association, its chairman says.
Mr Cameron made the statement at Prime Minister's Questions after Labour MP Joan Walley urged him to back a ban on pesticides harmful to bees.
Peter Chaunt, of Oxfordshire Beekeepers' Association, confirmed he was ex-president but had resigned.
In response, Number 10 said the PM has had "long and happy" links to the group.
Mr Cameron was quizzed by Ms Walley, who is chair of the parliament's Environmental Audit Committee, in the House of Commons on Wednesday.
His reply, in which he said he had been "neglecting his duties" at the association, led to some Labour MPs to shout "resign".
"If we don't look after our bee populations very, very serious consequences will follow," he concluded.
Mr Chaunt said while Mr Cameron's comment may have been a slip of the tongue, he had actually served as president of the association, which is based within his Witney constituency.
"When he became prime minister he wrote to us to say that with his new post he would be rather busy, and obviously beekeeping wasn't going to be at the forefront of his activities," Mr Chaunt said.
"He was coming up to the end of his period of presidency so we wrote back and thanked him very much because he'd been very helpful.
"He used to send us all the correspondence whenever the subject of beekeeping was raised in the Houses of Parliament."
In a statement, Number 10 said: "The prime minister has a long and happy connection with the Oxfordshire Bee Keepers' Association.
"For some years he was honorary president. This position recently came to an end.
"The prime minister is a strong advocate of beekeeping in his constituency and as he said in the house it's important we look after our bee population."
Mr Chaunt said he had written to Mr Cameron informing him of the error.
The new president is BBC Countryfile presenter John Craven.
Beekeepers and their supporters protested in Parliament Square on Friday to call for the government to support a ban on neonicotinoid pesticides linked to the death of bees.
The protest came ahead of a vote on a European Union proposal to ban the use of the chemicals.
Friends of the Earth's head of campaigns Andrew Pendleton said: "Mr Cameron may not be life patron of Oxfordshire beekeepers, but if he takes decisive action to safeguard Britain's threatened bees he will be performing an even more important beekeeping role."