The number of referrals from the NSPCC about child abuse has increased by 79% since the UK-wide lockdown was imposed, according to the charity’s data.
Calls to its helpline resulted in 923 referrals to police and social services between April and November.
Almost a third related to neglect and the charity warned more children could be at risk over Christmas.
Wales’ children’s commissioner said the pandemic had a “real and significant” impact on the most vulnerable children.
One caller to NSPCC Cymru’s hotline reported concerns their neighbour’s son was being neglected.
They said they could hear the father screaming and shouting obscenities towards his three-year-old son.
“This led to the boy crying constantly. The parents have no concern for their child, I’ve noticed the boy is regularly left in the garden for hours on end unsupervised,” said the caller.
“There is also an excess of bin bags all ripped in the back garden. I only noticed this because of the smell that was emanating from it. It makes me sad and upset seeing the boy treated like this.”
A mother also called as she was worried about her own son, who lived with his father.
“The father is unable to have a proper conversation about anything. The house is always a mess with lots of rubbish everywhere and my son is normally left to fend for himself,” she said.
“I’m worried about the impact this is having on his emotional wellbeing. I can’t keep quiet about this anymore, it’s really worrying me, what should I do?”
There was an average of 115 referrals from helpline calls made each month between April and November, compared to the pre-lockdown average of 64.
NSPCC analysis of the data showed the level of concern about emotional abuse, neglect and physical abuse remained well above the pre-pandemic average across the UK.
Kamaljit Thandi, head of the NSPCC helpline, said: “It’s no secret that this Christmas is going to be a very different one and, for thousands of children, being stuck at home for the holidays will be a terrifying thought.”
Children’s commissioner for Wales, Sally Holland, said people should trust their instincts and not delay speaking up.
“During a year where many have spent long periods unable to socialise with friends and unable to attend their nursery, school or youth group, some children will have spent more time in a home where they do not feel safe.
“With infection rates so high in our communities and no clear timeframe for getting back to normal life, it’s even more important than usual that people look out for signs of child abuse and contact their local child protection team, or Childline, if they are worried.”
NSPCC Cymru has urged the Welsh Government to encourage the public to be extra vigilant, especially during the Christmas holidays and while schools are closed, to ensure children and families “get the help they need”.
It also said the government needed to invest long-term funding to support children recovering from adverse and traumatic experiences during lockdown.
The Welsh Government said it was committed to working with safeguarding partners to do everything possible to prevent and tackle child abuse and to support children who have experienced it.
“Our national action plan sets out clear actions to prevent child sexual abuse, to protect children at risk and to support abused children.
“It was published in 2019 and actions are to be completed by 31 December 2021. The existing plan sets out the next steps which would then be taken, including considering evidence from a review of its implementation, in consultation with stakeholders, to decide on next steps.”