The Conservative party has apologised for sending a campaign letter addressed to "Mr Youmustbe F******joking" to an elderly couple.
Pictures posted online by Laura McCormack show a letter, purportedly from Prime Minister Theresa May, which was delivered to her neighbours in south London in February.
In the accompanying Twitter post, she writes: "Trying to argue they can run the country when they can't even work mailmerge. My elderly neighbours were more than a little upset to be addressed in this manner by the PM."
Ms McCormack then added a further photo showing a campaign donation form, also addressed to "Mr Youmustbe F******joking".
The couple are not party members and have no idea why they received the letter, according to Ms McCormack.
A Conservative spokeswoman told the Press Association: "It is unacceptable that this letter was sent out and we apologise for any offence caused.
"We are currently investigating this matter to ensure it does not happen again."