Jones 'extremely angry' over Welsh Labour staff briefing
Carwyn Jones is "extremely angry" about briefing against Welsh Labour staff, his spokesman has said.
BBC Wales was told the first minister believes any interference from the UK party with the way Welsh Labour is run would be "absolutely unacceptable".
WalesOnline suggested earlier this week that two Welsh Labour staff may be sacked if Jeremy Corbyn is re-elected.
Mr Jones said the individuals concerned helped "defy expectations" in election results.
The spokesman said: "Carwyn has made it clear he won't be publicly backing any candidate - he's stuck to that in previous leadership elections, and he's set out the reasons why on numerous occasions.
"However, it is right to say that he's extremely angry about the briefing against Welsh Labour staff.
"These are loyal, hard-working, committed individuals who recently helped defy all expectations with another clear Welsh Labour victory in the assembly elections.
"Carwyn is very clear that any interference with the way Welsh Labour is run would be absolutely unacceptable, and he will be writing to both leadership candidates asking for their public support for Labour staff."
The statement came after ex-minister Leighton Andrews told the BBC Good Morning Wales programme: "Carwyn must be furious about the briefing, the Corbyn-inspired briefing against senior Welsh Labour staff this week.
"This Welsh Labour staff have delivered two election victories for Carwyn Jones, and I can only imagine how angry he will be at the briefing that's been taking place suggesting they should be removed."
During the radio interview Mr Andrews, who is backing Mr Smith, said: "I don't think myself that Carwyn is going to come out of this as a supporter of Jeremy Corbyn.
"I imagine, I don't know, he hasn't told me this, but I imagine he would vote for Owen Smith."
But Mr Andrews, who previously served as education minister and public services minister under Mr Jones, said he would be "surprised" if Mr Jones would take a position on the leadership contest.
He said: "I think if Jeremy Corbyn wins again the Labour Party will not win a general election again for 15, maybe 20 years."
Mr Jones has not stated who out of Mr Corbyn or Mr Smith he would back in the current contest. However he has said it would be very difficult for him to carry on as a leader if he faced the same situation as Jeremy Corbyn.
Mr Corbyn lost a no-confidence vote of Labour MPs in June.
Mr Jones told The Wales Report that in the current situation Labour had "no chance" of winning a general election.
A Welsh Conservative spokesman said: "The first minister is taking a craven stance in not nailing his colours to the mast and picking a candidate for the leadership race."
They pointed out that London mayor Sadiq Kahn and Scottish Labour leader Keiza Dugdale had come out in support of Owen Smith. He added: "So the first minister's silence on this critical issue seems strange, and betrays a lack of leadership."
Analysis by Nick Servini, BBC Wales political editor
Until this point, Welsh Labour has largely managed to avoid getting sucked into much of the blood-letting currently on display among the different wings of the Labour Party.
There must now be a risk that it might.
Carwyn Jones has refused to give any endorsements to the contenders.
But his former Welsh Government colleague Leighton Andrews has said "why look into the crystal ball when you can read the book".
In other words, he believes it is obvious that Mr Jones is not a supporter of Mr Corbyn if you read between the lines of what he has said in recent months.
The briefing earlier in the week has clearly caused bad feeling. The message from Welsh Labour to the Corbyn camp is to stay well away from the way the party is run in Cardiff.
Jeremy Corbyn supporters say he is not a vindictive man and that while there may be some casualties within in the party in London if he wins the contest, it is unlikely that any purge would stretch to Wales.