Former senior immigration officials have spoken out against Peter Dutton's decision to free two foreign nannies from immigration detention.

French au pair Alexandra Deuwel was freed in October 2015, after her prospective employer's cousin, AFL boss Gillon McLachlan, requested Mr Dutton's assistance.

A few months earlier, Mr Dutton ordered Italian nanny Michela Marchisio be released, after lobbying from her proposed boss, a policeman Mr Dutton worked with in Queensland.

Former Immigration Department official, Viviana Barrio. ( ABC News )

Viviana Barrio worked for the Immigration Department for 23 years, including three years in charge of immigration at Melbourne Airport, where she regularly detained tourists she suspected would try to work.

"In 23 years, I've never seen a minister grant a tourist visa to an au pair," she told 7.30.

"A minister should not be intervening in these kinds of cases. Intervention powers are very valuable.

"It's a lack of respect for the system that allows for compassionate circumstances in very extreme cases, not these kinds of cases."

Ms Barrio also spent five years in charge of ministerial intervention cases for three states.

"I decided to talk to you because I feel that the public is being told that these cases are similar to the other cases … but these cases are not like any other one," she said.

"They're quite different."

'Impartiality guidelines don't seem to apply to ministers'

Until last year, Greg Phillipson was a senior lawyer in the Immigration Department, where he served for nearly 40 years.

"It would be quite unusual for the minister to intervene [in tourist matters] because normally the worst that can happen is that the person's visit to Australia is cut short and they go home," he told 7.30.

He said if Mr Dutton was a departmental official, he would not have been able to decide the cases because of a perceived conflict of interest.

Former Immigration Department lawyer, Greg Phillipson. ( ABC News )

"The usual situation is you declare the interest and you say it's not appropriate for me to make this decision because I know these people," Mr Phillipson said.

"It seems like these sort of impartiality guidelines don't seem to apply to ministers."

Mr Dutton declined to be interviewed for this story, but said in a statement each case was considered on its merits.

"There are long-standing intervention powers provided to ministers under the Migration Act. Any person is able to request ministerial intervention," he said in the statement.

"I have never met the individuals involved in one of these cases and in the other I worked with one individual in my former career as a police officer 20 years ago. To suggest that I have any personal connection or relationship in either case is false and misleading."

Dutton unlikely to appear at Senate investigation

A Labor-led Senate inquiry is investigating Mr Dutton's decisions and holding its first hearing today.

It has requested Mr Dutton and his staff appear, but he is not compelled and his name does not appear on the witness list.

Mr Dutton's office declined to comment on whether he would attend.

Senior immigration officials will be answering questions, as will the AFL's McLachlan and his head of government relations, Jude Donnelly, who emailed Mr Dutton's office.

Labor senator Kimberley Kitching said Mr Dutton needed to explain.

"I think until he does, there will be people questioning his integrity," she told 7.30.

"We have invited him, we are still waiting for him to respond.

"We have asked the relevant staff in his office to come. They haven't responded either."