One of the foreign au pairs Peter Dutton saved from deportation came to Australia to work for the family of a former police force colleague, Guardian Australia understands.

Dutton used his ministerial powers under the Migration Act in June 2015 to grant a visa to an Italian au pair who was intending to work for a Brisbane family.

The couple have worked for the Queensland police service and have two young children. The Guardian has decided not to name them.

The matter is one of at least two au pair visa cases which are now the subject of a Senate inquiry.

Guardian Australia revealed on Tuesday that Dutton had saved another au pair from deportation, intervening after the AFL chief executive officer, Gillon McLachlan, raised the young woman’s case on behalf of his relatives.

An email chain was leaked on Thursday featuring the correspondence of immigration officials, Peter Dutton’s office, an AFL staffer, McLachlan and his second cousin. The emails run over 14 pages and indicate that Dutton overruled border security advice and allowed entry to Australia for the French woman, Alexandra Deuwel, on 1 November 2015.

In the Queensland case, the Italian au pair had her visa cancelled upon arrival at Brisbane’s international airport on 17 June 2015. She was able to make a phone call and soon afterwards Dutton approved a new visa.

There are pictures on her Facebook profile showing she ate Tim Tams and Caramello Koalas on her first night in Australia, after the visa dramas were resolved. “First night in Australia.. FINALLY!” she wrote.

She later visited Surfers Paradise, Brisbane’s agricultural show the Ekka, Australia Zoo, Melbourne, and posed for pictures by the Brisbane River.

The au pair’s case file names the Brisbane family as her hosts, a source told Guardian Australia.

Dutton was a police officer from 1990 until 1999 before being elected to federal parliament in 2001. In 1997 Dutton and the family’s father completed a surveillance course together and were pictured in a group photograph.

Asked if the au pair was intending to work for his family, the policeman told Guardian Australia: “Not confirming, not denying. Just talk to Peter Dutton’s office. It’s well above my call as to what to say.”

The visa status of two au pairs have been in the spotlight since March, when it was revealed Dutton granted them visas on public interest grounds.

“There were two young tourists who had come in on a tourist visa and declared … [they] intended to perform babysitting duties while here,” Dutton told parliament in March.

“The decision that was taken … that those two young tourists would be detained and that they would be deported. I looked into the circumstances of those two cases and I thought that inappropriate.”

A former immigration department official said what horrified frontline airport personnel most about the au pair cases was that their decisions were being “overruled so quickly and at such a senior level”.

A Senate inquiry is investigating the au pairs’ visas and is due to report back to parliament on 11 September.

In response to questions about the Brisbane and Adelaide cases, a spokeswoman for Dutton said that as immigration minister he had received hundreds of representations on individual migration matters from MPs, journalists, members of the public and others every year.

“Ministerial intervention powers have existed under Labor and Liberal ministers for many years, to be used in cases where special circumstances exist according to the law,” she said. “Suggestions that somehow there is impropriety or some personal gain is completely false.”

Dutton released a separate statement in relation to the Guardian’s story on the Adelaide au pair, saying: “I consider cases on their merits. Any suggestions cases are determined on any other basis, including whether I knew the individual who referred the matter, is completely ridiculous.”

On Thursday he defended his decision on 2GB radio. “I looked at it and thought it’s a bit rough, there’s no criminal history, she’s agreed that she wouldn’t work while she was here,” he said.

“As I understand it, she never overstayed the visa, hasn’t committed any offences, and I thought it was an application of common sense.”

Labor’s immigration spokesman, Shayne Neumann, called on Dutton to explain himself: “As each day goes by, there are more serious questions Peter Dutton needs to answer about the use of his ministerial powers.”

After the release of the emails Dutton put out a statement defending his decision to overrule departmental advice.

“By definition, given the department has made a negative decision, they don’t advise me to change their decision,” he said. “I make decisions on the merit of individual cases according to the law.”

Meanwhile, the managing director of the AIFS Au Pair agency, Wendi Aylward, seized on the saga, calling for a special visa to be set up.

“A dedicated au pair visa will ensure there is tighter regulation around the recruitment, screening and support of au pairs and Australian families,” she said.

She said au pairs were the preferred childcare option for an increasing number of Australian families.

“We hope that the attention on minister Dutton’s decision will shine a spotlight on the au pair sector and give Australian families much-needed certainty about this growing childcare option.”