The government's most senior female figure, Foreign Minister Julie Bishop, has come to the defence Prime Minister Tony Abbott's top aide, Peta Credlin, whom a senior party official dubbed the "Horsewoman of the Apocalypse".

The reference was made by the Liberal Party's honorary federal treasurer, Phil Higginson, who recently made headlines after an explosive letter he wrote complaining about Ms Credlin's position was leaked to the media.

Tony Abbott in discussion with his chief of staff Peta Credlin. Credit:Alex Ellinghausen

In that letter, Mr Higginson complained that the Liberal Party had allowed a married couple to virtually control all elements of the party by allowing Ms Credlin to be the Prime Minister's powerful chief of staff while her husband, Brian Loughnane, was also federal director of the party's administrative arm.