Peter Dutton, the driving force behind a bitter Liberal party coup that unseated Malcolm Turnbull as prime minister last week, has strongly denied any wrongdoing.

But the scandal is deepening with a Senate committee inquiry due to scrutinise his decisions next week at the request of opposition politicians.

In the first case Dutton, then immigration minister and known for his support of hardline policies, used his discretionary powers to free a Frenchwoman from detention in November 2015 and allow her to stay in the country.

The move was made after an appeal to his office by Australian Football League boss Gillon McLachlan, documents released under freedom of information showed.

The woman was reportedly planning to work as a live-in babysitter for a relative of McLachlan, but did not have the proper paperwork when she arrived.

National broadcaster ABC and other media said Dutton’s intervention also helped a wealthy family that was also a Liberal party donor.

The Labor opposition party has been demanding to know whether their political donations influenced his decision to free the woman.

A second case emerged on Thursday involving an Italian au pair.

That woman was detained at Brisbane airport, also in 2015, because border force officials believed she planned to work as a babysitter in breach of her tourist visa.

Dutton overruled the decision which benefitted the family of a man he used to work with when he was a police officer before entering politics, according to leaked documents cited by ABC and other media.

Critics have contrasted the cases with Dutton’s unwavering commitment to keeping asylum-seekers in overseas detention under Canberra’s hardline immigration policies.

But Dutton on Friday insisted they were “common sense” decisions.

“I make a decision that I believe is in the best interest of our country. I do it every day with visas,” he told commercial radio 2GB.

“That’s the whole reason for ministerial intervention, because you believe the department has made a decision that is not right.”

He added in a separate statement that he dealt with hundreds of representations over immigration matters every year.

“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.”

But Labor immigration spokesman Shayne Neumann said the public would be stunned by the “troubling pattern” of interventions.

“It’s not about the powers, it’s about the process,” he said, adding that most people would have expected the au pairs to be “put back on a plane and deported”.

Dutton, an arch conservative, launched a leadership challenge against moderate Turnbull last week, but was defeated by Scott Morrison in the race to become prime minister.

Senior Labor frontbencher Anthony Albanese suggested the leaks about the au pair cases were “payback for his role in wrecking the Liberal Party last week”. DM