One of the UK's largest mobile network providers is advising parents not to give primary school-aged children their own smartphone.
EE, which is owned by BT, said it aims to improve children's "digital wellbeing" after receiving increasing requests for guidance from parents.
It said that under-11s should be given "non-smart" devices that have similar capabilities as old brick phones.
The recommendation - announced for the start of the new school year - comes amid growing concern about the effects of smartphone and internet usage on children's mental health and behaviour.
Access to the internet can support young people's education and social activities, as well as helping parents keep track of their whereabouts.
But, some experts warn it contributes to shorter attention spans, exposes children to harmful content, and displaces other activities such as playing outside or talking to friends.
EE said under-11s should be given phones that can be used to text and make calls, but without access to the internet or social media apps like TikTok and Youtube.
The firm, which is marketing a phone with limited capabilities for children, suggests parents use apps and settings to monitor older children's internet usage.
Its corporate affairs director Mat Sears said EE wanted to help parents and caregivers "make the best choices for their children".
He told the BBC: "Under-11s we feel should not be given access to smartphones. They don't need the usage of a smartphone and, actually, a feature phone - or a dumb phone, as some people call them - is more suitable."
Almost a quarter of five-to-seven-year-olds now have their own smartphone, recent research from the telecoms regulator Ofcom found.
By age 11, when children typically transfer to secondary school, almost all have a phone of some kind, it says.
Ofcom described its research, published earlier this year, as a "wake-up call" after it found over half of under-13s were using social media, despite most of the big platforms having rules requiring that users are over 13.
Mr Sears said he believed smartphones were appropriate for children aged between 11 and 13 - but not access to social media.
For 13-to-16-year-olds, he advised parents to exercise "care and attention" over which social media apps they download.
"We think it's absolutely fine and okay for social media to be used [by over-13s] but various parental controls and privacy settings should be put in place, as well as screen locks for the amount of time that is being placed on these various social media sites."
Clare Fernyhough, co-founder of grassroots campaign group Smartphone Free Childhood, welcomed EE’s new guidance.
“It’s a positive move to get parents to question this norm that ‘yeah I’ll just get them a smart phone'," she said.
Ms Fernyhough continued: “I would challenge the idea all children need a phone.
“[But] if a child needs a phone at all, absolutely it should be a simple phone. They are far less addictive.
“The way smartphones are, they are adult devices, they are not safe for children."
She would like to see a mechanism introduced for verifying a person’s age on the device itself, not just when signing up to access content, as is the case now.
Recent government legislation aims to ensure children are not exposed to harmful online content, such as material that promotes suicide and self-harm, eating disorders, and violent content.
The Online Safety Act places more responsibility on technology platforms, introducing a legal duty of care towards their users.
But the Act does not come into force until 2025, and critics, including Ms Fernyhough, say while it is a step in the right direction it does not go far enough to protect young people.
Some other countries, including France, Italy and the Netherlands, have banned the use of smartphones in schools.
Last year, China's regulator proposed limiting daily screen time for children up to the age of 18.
The UK's Commons education committee said in May that the government should consider a total ban on smartphones for under-16s.
Prime Minister Sir Keir Starmer said in July that he does not support "simply banning" phones for under-16s, but that the government needed to "look again" at what content children were accessing online.
Last year, parents from eight primary schools in County Wicklow, Ireland, agreed not to give their children smartphones before they went to secondary school to relieve the peer pressure from other children already having access.
