New research shows that 28% of Irish children have experienced cyberbullying during the lockdown - among the highest rates in Europe.
A joint study between the European Commission and researchers at Dublin City University found rates were highest in Ireland, followed by Italy and Germany.
The younger children were, the more likely they were to become victims, the study found, with the problem particularly prevalent in young boys.
Tijana Milosevic, of the National Anti-Bullying Research and Resource Centre, said the results are higher than in previous studies.
She said: "Irish children are among the top frequency numbers in Europe that we have. That is worrying in and of itself.
"This was a survey that was done with children in 10 other European countries with children aged 10 to 18.
"We conducted research into their use of digital media but also their experience of risks and their exposure to different types of online harm, cyberbullying being one of those.
"We see a 28% increase in cyberbullying victimisation during the lockdown."
The findings were presented to the Oireachtas Committee on Education to mark the UN International Day Against Violence and Bullying in Schools.
Overall, 49% of males had experienced significantly more frequent cyberbullying since lockdown.
About 66% of all children between 14 and 16 experienced significantly more cyberbullying compared with pre-lockdown on instant and private messaging services such as WhatsApp, Viber and Telegram.
Dr Milosevic said: "This is an increase compared to previous studies in Ireland, which have shown a cyberbullying victimisation rate of about 14% for primary schools and just under 10% for post-primary schools.
"There has been an increase, but it's not as huge of a spike as we might have expected based on media reports we were seeing during the lockdown."
She said social media platforms had to do more as the lines between in-school bullying and cyberbullying become increasingly blurred.
"It's different now, especially in the context of Covid, when a lot of the schooling has happened online - the line between school bullying and out-of-school bullying will become ever more blurry.
"It is extremely important to have a way to actually report and engage the platforms to assist cases when it does happen."
Seline Keating, a professor and research fellow in anti-bullying studies at DCU, called for a single anti-bullying programme to be implemented in schools nationwide.
She warned that current measures, adopted in 2013, were not being fully implemented in some schools - particularly in relation to identity-based bullying such as homophobia and transphobia.
She told the committee: "Some schools may adopt an a la carte menu when dealing with bullying.
"They may not have the confidence or skillset to tackle the transphobia or homophobia elements. So they pick and choose which types of bullying to address."
There should be a mandatory component to keep written records of all reports of bullying in schools, Dr Keating said, adding: "If schools are consistent with recording all incidents, that will highlight patterns to a school.
"They can see at the end of the school year, oh cyber bullying is a huge issue, this keeps coming up.
"They can see that identity-based bullying, racism, seems to be prevalent in our school in the last year, we need to tackle this.
"But by not recording bullying incidents, by not having records of what has happened, schools don't have the opportunity to see the pattern."