Tony Abbott's most senior adviser was charged with drink-driving on the night the Opposition Leader delivered his budget reply speech.

Mr Abbott's chief of staff, Peta Credlin, blew over the legal limit on her way home from a dinner in Canberra last Thursday night.

Several functions were held after the speech, including at least one at Parliament House.

Mr Abbott has brushed aside a question about whether he would take any action against Ms Credlin, saying she is an "outstanding chief of staff".

"She accepts that she's made a mistake, she's done the wrong thing," he said.

"She will now go through the ordinary process that every Australian in this position goes through.

"I stress this is something that happened in her time, in her private time.

"She does an absolutely outstanding job as my chief of staff."

A spokesman for Mr Abbott says she "recorded a low-range reading" but would not reveal the exact figure.

"She accepts without reservation that she has done the wrong thing and the matter will be dealt with in the usual way," the spokesman said.

A low-range reading in the ACT is regarded as between 0.05 and 0.08 and does not result in an immediate suspension of an offender's license.

However, it does still require a court appearance.

Ms Credlin is married to Liberal party director Brian Loughnane.

ACT Police say a 42-year-old woman recorded a reading of 0.075 in the Canberra suburb of Barton on Thursday night.

Last month, Mr Abbott demoted his chief policy adviser over what he has described as a "drunken brain snap" after an incident at a corporate function.