A woman stands in a flowing white dress while a man holds her wearing a dark suit – the photo immediately appears like any portrait of a newly-married bride and groom.

But it is of a young girl with her father, preparing to make an entirely different pledge: one of virginity at a “purity ball”.

Swedish photographer David Magnusson took the evocative portrait as part of his “Purity” series of images capturing fathers and daughters joining the conservative Christian movement in the US.

He spent five months on four different trips in the country meeting the girls swearing to abstain from sex until marriage and their families.

Purity by David Magnusson Show all 9 1 /9 Purity by David Magnusson Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse Purity by David Magnusson Purity David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' David Magnusson - do not reuse

He said his interest was sparked by an article about so-called purity balls, which have spread across 48 states, where fathers and daughters make pledges to each other committing to “live pure lives before God”.

“When I first heard about the purity balls I imagined angry American fathers terrified of anything that might hurt their daughters or their honour,” Magnusson said.

“But as I learnt more, I understood that the fathers, like all parents, simply wanted to protect the ones that they love – in the best way they know how. It was also often the girls themselves that had taken the initiative to attend the balls.

“They had made their decisions out of their own conviction and faith, in many cases with fathers who didn’t know what a purity ball was before being invited by their daughters.”

David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' (David Magnusson - do not reuse)

The photographer left Stockholm to visit Colorado Springs, where the phenomenon started in 1998, and Shreveport in Louisiana.

Magnusson attended two purity balls, watching girls in Colorado walk in their ball gowns to place a white rose in front of a wooden cross as a symbol of them giving their virginity to God.

He told The Independent how the balls had a structure similar to traditional white weddings, with formal dinners, speeches, vows and dancing.

“To them the ceremonies were a very serious thing but they still seemed to have a lot of fun,” he added.

“The youngest girls I saw were one and four but they weren't expected to make any promises about their sexuality. It was more about the fathers.”

The average age of girls Magnusson saw was around 12 or 13, the start of puberty.

He interviewed 28 fathers and daughters and photographed them for his book, Purity, which was published last year.

“I wanted to take a series of portraits that were so beautiful that the girls and their fathers could be proud of them but that may provoke a completely different reaction from people viewing them,” he told The Independent.

Magnusson said he was “fascinated” about the marital symbolism of the clothing, vows and balls.

He was initially shocked by the movement but after meeting the families, he said it appeared not to be just about sex, but about father-daughter relationships.

He added: “The balls were founded in conservative, Christian circles where fathers might be the breadwinners and they have very traditional family roles.

“Kids might not see their fathers that much….fathers felt there was some kind of need to be more present in the lives of their daughters and be an example of the kind of husband they are looking for.”

David Magnusson photographed fathers and daughters taking part in 'purity balls in the US' (David Magnusson - do not reuse)

The concept may sound old-fashioned but it is little over 20 years old and spreading fast, apparently as a response to the perceived sexualisation of young girls in society.

The Wilson family, who founded purity balls in Colorado, describe the balls as “an event that celebrates the incredibly important father-daughter relationship”.

In their format, fathers sign a pledge committing to be the “example of purity and model integrity for their daughter's lives” and the girls “silently commit to live pure lives before God”.

The Christian Center, which organises purity balls in Illinois, claims it “holds high the banner of purity in the midst of a culture that destroys it”.

“We hope you will join us as we encourage young women to commit to moral purity and help them understand the beautiful and righteous life God offers them,” a statement on the group’s website continues.

“The Bible lays the responsibility of protecting daughters at the feet of their fathers. We desire to charge men to take up this mantle of responsibility!”

Purity has been exhibited in several countries (David Magnusson - do not reuse)

Magnusson hopes that people who view his portraits can try to understand the people in them, whether they agree with the practice or not.

He said: “To me, Purity is a project about trying to understand how we are shaped by the society we grow up in and how we interpret the world through the values we incorporate as our own.”

The project has been exhibited at galleries in Stockholm in Sweden, Helsinki in Finland, Hyeres in France, and Los Angeles in the US.