Dr Zoe Hilton, the National Crime Agency's (NCA) head of child protection, told MPs it was now normal for teenagers to text sexually explicit messages and photographs to each other because they want to emulate stars.
Speaking to the Commons Education Committee, Dr Hilton said: "Obviously children and particularly older children are looking at celebrities [and] are looking at what the adult population are doing.
"I think we've got to the point with older teenagers where sexting is actually a normative behaviour.
"Actually what we need to do is get them to recognise when it's abusive, when it's harmful, when it's linked to exploitation, when it's linked to the beginning point of an exploitative relationship.
"But I think we also need to recognise that this is something that some young people will do regardless of all the safety messages in the world."
Her comments come amid mounting concern about the number of teenagers sending explicit messages to friends, boyfriends, girlfriends and in some cases complete strangers.
Last year the NSPCC warned that 'sexting' is now common among adolescents, with 40 per cent of young people admitting to creating sexual images and videos of themselves and 25 per cent saying they had sent them via text message.
Earlier this week Home Secretary Theresa May warned that sending a single 'sext' or sexual online message to an under-16 could become illegal.
She has asked officials to carry out an 'urgent' review on whether the law needs to be tightened.
At the moment, there is no specific offence against an adult sexual messaging with under-16s, except when it contains graphic images, or if an adult attempts to meet up with their victim to engage them in a sexual act.
Last week, Kim Kardashian's habit of posting explicit sexual images of herself on the internet was blamed for encouraging young girls to do the same and making them vulnerable to online predators.
At an NSPCC debate, Nazir Afzal – the chief prosecutor for the North West of England who helped bring the Rochdale grooming gang to justice in 2012 for abusing up to 47 girls – said the reality TV star was tempting young girls into sexualising themselves and presenting opportunities to predators.
Mr Afzal said: "The sexualisation of children does not help. The reality is that younger and younger children these days are now exposed to the kinds of things, I saw Kim Kardashian a couple of days ago [the magazine images].
"It's those kinds of things, role models out there saying this is the way to live your lives. But unfortunately, [predatory] men want that to happen, want them to believe that's the way to be, that men can interfere with them and damage them in some way."
Do you think children are influenced by celebrities or more by their peers?