Julie Bishop says 'Horsewoman of the Apocalypse' comments about Peta Credlin are regrettable

Foreign Minister Julie Bishop says it is “deeply unfortunate” that a text message reportedly written by the Liberal Party treasurer describing chief-of-staff Peta Credlin as the "Horsewoman of the Apocalypse" has been made public.

The ABC reports that the confidential text message, allegedly written by Philip Higginson and sent to a senior Liberal figure last year, has been leaked to the station's Four Corners program.

Higginson also reportedly wrote, "I do hope you can negotiate the removal of Credlin. That would be a huge win in itself."

It follows an explosive email from Mr Higginson that was leaked to the media last month, in which he criticised the Liberal Party for allowing an alleged conflict of interest involving Ms Credlin and her husband, federal director Brian Loughnane.

When Ms Bishop addressed the media this morning, she described the most recent leak as regrettable.

"Of course it's always unfortunate if there are leaks to the media that are damaging to any political party, that's not a desirable outcome," Ms Bishop said.

“I'm not aware of the details of these text messages but anything of that nature is obviously most unfortunate and shouldn't be said.

When pressed on the text message on Sky News later in the morning, the Foreign Minister added, "It's very colourful language, it's deeply unfortunate that it was said, that it's been made public."

"The less we talk about ourselves and the less that the internal workings of the Liberal Party are made public, the better off for everybody," Ms Bishop said.

Mr Higginson's initial "letter of concern" to the party's 27-member executive committee mentioned his "good friend" Tony Abbott and the "sheer vitriol and pent-up animosities" he claimed were affecting the Prime Minister's relationships within the party.

It's been reported that these issues Mr Higginson raised came to a head during the failed attempt to oust the Prime Minister from office in February.