Federal Small Business Minister Michaelia Cash insists she has provided a witness statement to police about raids on union offices — despite the Australian Federal Police (AFP) saying she did not.

Key points: Michaelia Cash said she fully cooperated with the Australian Federal Police

Michaelia Cash said she fully cooperated with the Australian Federal Police The Senator claimed "you [couldn't] get better evidence than what I provided... under oath"

The Senator claimed "you [couldn't] get better evidence than what I provided... under oath" However, the police insist Senator Cash was not forthcoming with a formal statement

Senator Cash has been under pressure because her staff tipped off the media that police were raiding the Melbourne offices of the Australian Workers' Union back in 2017.

The raids are now the subject of a civil court case and Senator Cash appeared as a witness last week.

In Senate estimates on Tuesday, Labor senators grilled Senator Cash over whether she had cooperated fully with police.

The AFP has said it asked Senator Cash and her colleague, Michael Keenan, for formal witness statements to help with investigations into the leaking of plans to raid the Australian Workers' Union's offices.

But police said neither minister was forthcoming.

However, Senator Cash told the estimates hearing she did provide a statement.

She said she sent police a transcript of previous answers she had given to Senate estimates.

Federal officers raided the Australian Workers' Union in 2017. ( AAP: Julian Smith )

"That was my statement to the AFP, to refer them to my comprehensive estimates Hansard, as five months after the event it was my best recollection of events," Senator Cash said.

"I also note that the AFP came back with no further request for information in relation to the statement I provided."

But earlier this week, AFP Deputy Commissioner Leanne Close told Senate estimates that was not technically a witness statement.

So, Labor Senator Murray Watt asked Senator Cash how they could both be right.

"Who's telling the truth — you or the Deputy Commissioner of the Australian Federal Police?" Senator Watt said.

Who's who in the witness box: Senator Michaelia Cash: WA Senator who was the Federal Minister for Jobs at the time. She has repeatedly and vehemently denied knowledge of the media tip-off, which came from her office.

WA Senator who was the Federal Minister for Jobs at the time. She has repeatedly and vehemently denied knowledge of the media tip-off, which came from her office. David De Garis: Senator Cash's media advisor at the time who admitted to tipping off the media, and resigned. He now works for the Australian Hotels Association based in Perth.

Senator Cash's media advisor at the time who admitted to tipping off the media, and resigned. He now works for the Australian Hotels Association based in Perth. Mark Lee: Media advisor at the time at the Fair Work Ombudsman which also assists the Registered Organisations Commissioner. He was formerly a media advisor to the former Victorian premier Denis Napthine. At the time of the raids he was expecting to join Senator Cash's office as a media advisor, but after the raids that did not happen.

Media advisor at the time at the Fair Work Ombudsman which also assists the Registered Organisations Commissioner. He was formerly a media advisor to the former Victorian premier Denis Napthine. At the time of the raids he was expecting to join Senator Cash's office as a media advisor, but after the raids that did not happen. Ben Davies: Chief of staff for Senator Cash at the time. He left the office a few months later. In 2011, he worked in the office of Victoria's then attorney-general, Robert Clarke.

Chief of staff for Senator Cash at the time. He left the office a few months later. In 2011, he worked in the office of Victoria's then attorney-general, Robert Clarke. Chris Enright: Executive director of the Registered Organisations Commission who wrote to the AWU two months before the raids advising of the ROC investigation

The Government solicitor, Michael Kingston, was asked for his advice on the difference between a "statement" and a "witness statement" on Tuesday.

But he said it was not his area of expertise and he did not want to weigh in without doing a bit of research.

The Minister also said she could not immediately answer many of Labor's questions because she was yet to read the full transcript of the AFP Deputy Commissioner's remarks in estimates on Monday.

When Senator Watt asked her why she had not read the transcript, she replied: "Because I haven't".

At one point — after Senator Watt offered to take Senator Cash down to the police station to make a statement then and there — the committee chairman shut down the hearing for an early tea break.

On Tuesday, estimates also heard Senator Cash had racked up more than $288,000 in legal fees over two financial years because of the AWU proceedings.

But the Attorney-General, Christian Porter, told Radio National it was standard protocol to cover ministers' legal costs in these situations.

"That is a very long-standing rule that has applied to (former prime minister) Kevin Rudd appearing before a royal commission into pink batts — it's applied to a whole range of circumstances," Mr Porter said.

Senator Cash said her appearance as a witness in court on Friday showed she was cooperating with the justice system.

"The AWU's barrister asked me questions and then cross-examined me on all of these events," she said.

"I don't think you can probably get better evidence than what I provided on Friday under oath in the Federal Court," Senator Cash claimed.

She also said Labor's ongoing attacks on her over the AWU raids had been proved to be unfair.

"I am waiting now for an apology."

The pressure will be back on when Senator Cash fronts estimates again later today.