The partner of the first openly gay foreign minister in Europe, and perhaps the world, knew defining his rather unique role could present a few challenges.

But Guido Westerwelle of Germany's longtime companion, 43-year-old sporting event manager Michael Mronz, has walked into a political firestorm just over four months since the new government took office.

The mild-mannered Mronz opted to accompany Westerwelle, who is also Germany's vice-chancellor, on a tour of Latin America as an official guest of the delegation this week following a swing through Asia together in January.

Despite opposition attacks over potential conflicts of interest and the obvious discomfort of some conservatives in Chancellor Angela Merkel's coalition, Mronz says he has no intention of dropping out of the ministry's frequent flyer club.

In the process, he is re-writing Germany's tradition-steeped diplomatic rule book.

"Mr Westerwelle and I travelled together regularly before the election," Mronz told AFP. "I don't see why we should stop now."

But Mronz this month suddenly found himself hit by accusations that he was piggybacking on official government business to scoop up new business deals.

Westerwelle was in Brazil for political talks, but also in a bid to lure lucrative contracts for German firms as the South American powerhouse gears up to stage the soccer World Cup in 2014 and the Olympic Games in Rio in 2016.

Mronz insisted he had not held a single business meeting while in Brazil, and as Westerwelle met with the organising committees of the two events in Rio de Janeiro, AFP was invited to accompany Mronz to a children's charity in a bitterly poor village a 90-minute drive from the city.

The hobby sailor was this month elected to the board of A Heart for Children, a charitable foundation sponsored by the country's top-selling newspaper, Bild.

The daily has been noticeably friendly to the often brash Westerwelle since he came under fire for damning comments about Germany's cherished welfare state. And a few years ago it voted Mronz one of the country's 50 most attractive men.

"Due to our life circumstances, we won't be able to have kids of our own so I am doing what I can to help the poorest of poor children," Mronz said, explaining his commitment to the charity.

"In countries like these, a little money goes a long way."

Westerwelle famously had his coming-out at Merkel's 50th birthday in 2004 with Mronz at his side. Asked if he saw himself in a historic role as half of a world-class gay power couple, Mronz demurred.

"We do not define ourselves by it," he said of their homosexuality. "I was simply raised to respect every person for who he is."

A few of Westerwelle's defenders have pointed to homophobia behind what his entourage sees as highly personal attacks but Mronz took the long view.

"Things have a way of working themselves out -- the accusations that are out there will clear themselves up."

The couple wear gold wedding bands on their left-hand ring fingers but Mronz said they have not entered into a "registered partnership", a status short of marriage that Germany offers to gay couples.

When asked whether they might tie the knot, Mronz said: "Those are issues that are not on the table and even if they were, we wouldn't discuss them in public."