There are a lot of contenders for most uncomfortable moment in Lindsay Lohan's upcoming BBC documentary about child trafficking in India, but I think the bit that will have most viewers kicking their televisions is when Lohan is hugging a very young girl on her knee, listening to her describe a life spent begging on the streets of Calcutta.

The shaven-haired girl is explaining that her parents would beat her unless she went out every day to earn money, but it's hard to concentrate on what she's saying because what's happening behind her is so distracting. Lohan is rubbing her already-red eyes, spreading mascara around the place, twitching her eyebrows.

"Um. Um. Oh my God," the film star says, her lips wobbling uncontrollably. A disembodied hand pops into the screen to pass her a tissue. "Um. How did she feel? Um. How did they treat her?" she asks, beginning to sob.

The small girl turns to look at her in bemusement. The translator gives an embarrassed laugh and says to the girl: "She's crying for you. Why don't you comfort her?" So we watch as the puzzled child dutifully strokes Lohan's long mane of golden hair.

"Oh my God! Oh my God!" Lohan says, with a husky gasp. "Sorry, I'm having a moment." Mercifully, the camera is then switched off.

The BBC has made a compelling film about the rising problem of child labour in India, explaining how the country's economic boom has fuelled a surge in demand for cheap, docile workers, which has sent traffickers rushing to the nation's most impoverished rural regions. A parade of young girls and boys give powerful accounts of how they were made to work 14 hours a day, ill-fed, and, on occasion, forced into prostitution. Campaigners criticise the Indian government for failing to tackle the issue. The material is potent and persuasive, and it's a great film except for the constant, distracting presence of Lohan, whose teary face keeps hoving into view, muttering horrified "wows".

Justifying its unexpected decision to hire Lohan (better known for what is euphemistically termed a party lifestyle) to front the documentary, the BBC argues that this is about creating a wider interest in poverty and development issues, and it's true that her involvement has whipped up a lot of pre-broadcast publicity. It is also true that most of this interest has focused on her, not on the issues, and has been wholly negative.

Child trafficking is a growing problem in India, so it would be great if a lot of people grit their teeth, watch the programme and feel inspired to do something about it. But don't take the actor's advice on the best way to show support. At the end of the film, a rather unwell-looking Lohan is not entirely sure what people should do to help, and suggests: "Twitter? There's Twitter . . ."

Better, I think, would be to give money to savethechildren.in