News of the couple's reunion broke after Phil revealed they had rekindled their relationship in an interview last month.
The couple got back together last year, and have been living together in Miami for the past six months.
The 64-year-old singer revealed the surprising news when asked about his struggle with alcohol addiction by Billboard, saying: 'I'm all right now. I bought a house (in Miami) about six months ago. I'm actually back with my third wife - I haven't really talked about it. We've been together for a while, and nobody's noticed.'
Now his ex-wife and current partner has told a Swiss newspaper that the two plan to tie the knot again, despite their £25 million divorce.
'I call Phil now again as my husband. We are so close that it makes no difference whether we are married,' Orianna told the newspaper. 'But we are determined to get married one day a second time.'
The couple first got married in 1999, in Switzerland
Phil and his ex-wife began rekindling their relationship when she was in the hospital due to complications in a surgery and he stepped up to take care of their children.
'We were always very close, because of the children... just last year, I realised that he is indeed the man of my life', Orianne explained. 'I spent four months in hospital, and he took wonderful care of Matthew and Nicholas. That was a great relief to me... we are meant for each other.'
Soon to become Mrs Collins for a second time, Orianne said she's started to plan the ceremony, but that this time the couple want a more intimate gathering, unlike their first wedding in 1999.
Phil and Orianne have two children together
'The important difference is that now our children can be there', Orianne said. 'I imagine the next celebration will be more familiar and smaller. On our first wedding in 1999 in Lausanne, we had to invite many more people to not disappoint anyone.'
Their first marriage lasted for seven years, and they have two children, Nicholas, 14, and Mathew, 11.
Phil already had three children from previous marriages - Joely, 43, and Simon, 39, with his first wife Andrea Bertorelli, and actress Lily Collins, 26, with his second wife, Jill Tavelman.
They announced their separation in March 2006 and two years later their divorce was finalised, with Phil staying in Switzerland and Orianne moving to Miami with their kids, after receiving £25million in the divorce settlement.
After their split, Orianne married banker Charles Fouad Mejjati and gave birth to their son, Andrea, who's now five years old.
Phil, who was born in London and has been three years sober, said he spent some dark times after his divorce.
'It started to be bad for my body. I almost died. My organs were beginning to shut down', he told Billboard.
We're hoping second time is a charm - all the best for the couple!