Hundreds of campaign leaflets for Conservative Party chairman Richard Holden have been sent to the wrong constituency, the BBC has been told.
It is understood the literature ended up at homes in a neighbouring Essex seat.
The party would not confirm how many had gone astray.
But it said such a mistake was not uncommon and was out of their control.
As party chairman, Mr Holden oversees national party administration and campaigning.
It is understood that some of his “election addresses” ended up in next-door Rayleigh and Wickford rather than the seat he is actually standing in, Basildon and Billericay.
An “election address” is where candidates can mail one addressed piece of campaign material to voters’ homes, using free postage.
Mr Holden told the BBC he thinks just a “few hundred” leaflets were misdirected but some local party insiders have suggested it is more like thousands.
The BBC hasn’t been able to fully establish how the error occurred, with Mr Holden pointing to possible administrative errors by postal services or the local council.
Royal Mail said: “The leaflets arrived at the delivery office addressed to households in Wickford and so were delivered accordingly."
Basildon Council said it had not sent any information directly to Royal Mail.
Privately some Tories in the area are blaming “data” errors by the party, locally or nationally.
It is almost as though CCHQ [Conservative Campaign Headquarters] has decided to “cock up everything” at this election, one told the BBC.
CCHQ confirmed some election addresses from Mr Holden went to the wrong houses, without saying how many.
The party told the BBC the mistake was not within its control but did not specify who it thinks is to blame.
Mr Holden is standing in Basildon and Billericay after his prior seat was abolished under a review of constituency boundaries.
Local Conservative officials were angered when central office put the party chairman forward at the last minute, as the sole candidate they could choose from.
Mr Holden was accused of trying to bag a “safe seat” that lies nearly 300 miles south from his old one of North West Durham.
However some have since praised Mr Holden’s approach, saying he has been “working hard” on the doorstep.
The seat, vacated by the incumbent MP who is standing down, had a 20,000 Conservative majority in 2019.
But as the Conservatives continue to lag well behind Labour in the polls, campaigners say the race is looking “close” and could go “down to the wire”, with fears they are bleeding voters to Nigel Farage’s Reform UK.
A full list of candidates for the Basildon & Billericay constituency can be found here.