Many teachers and parents have long been worried about what pupils get up to online, as well as the effects of long hours spent on phones and computers on their development.

In February, the House of Commons Science and Technology Select Committee launched an inquiry to gather evidence on this issue from the public, experts and tech companies themselves.

On Tuesday, the committee will question major social media firms, including Facebook and Twitter, on how they handle reports of inappropriate material on their platforms and the steps they take to remove illegal content.

They will also hear feedback on proposed new rules that would see social media companies regulated in much the same way as the mobile phone and broadband industry.

What is the inquiry about?

The committee is examining the effect of social media and screen use on young people’s health and wellbeing.

When it launched the inquiry, committee chair Liberal Democrat Norman Lamb said that it was "vital" for MPs to understand the services' long-term effects – "the benefits as well as the risks".

"We want to determine the scale of the issues – separating out the understandable concerns from the hard evidence – and to identify what practical measures people are already taking to boost the benefits and blunt the potential harms," he said.

"We want to hear from schools and young people, as well as from the industry and government."

Why now?

The inquiry is a response to a slew of research highlighting how widespread the use of social media is among pupils, and its potentially damaging effects.

An Education Policy Institute report, published last year, revealed that 95 per cent of 15-year-olds in the UK use social media before or after school, and half of 9- to 16-year-olds use smartphones on a daily basis.

The Royal Society for Public Health's 2017 #StatusOfMind report found that four leading social media platforms – Facebook, Snapchat, Instagram and Twitter – have a net negative impact on young people's health and wellbeing.

Meanwhile, the Life in 'likes' report, from children's commissioner Anne Longfield, found that children as young as 8 are experimenting with a variety of different social media platforms.

More recently, a poll of 20,000 pupils found that they are sharing jokes about rape, slavery and the Holocaust on social media accounts that are hidden from parents and teachers, as part of a growing “dark-meme culture”.

Who will speak?

Tuesday’s session opens with evidence from Karim Palant, the UK public policy manager for Facebook and Ed Balls' former policy chief. He may be rather wary to take the stand after receiving a humiliating dressing down from Labour MP Helen Jones when he appeared before a select committee in June.

He will be accompanied by Claire Lilley, Google’s lead on child safety in Europe, the Middle East and Africa (EMEA), and Sinéad McSweeney, vice president of public policy and communications for EMEA at Twitter, to discuss how they handle inappropriate content and regulation.

Afterwards, Will Gardner, the director of the UK Safer Internet Centre, and Sarah Hannafin, a senior policy adviser at the NAHT headteachers' union, will discuss digital literacy.

What's this talk of new regulation?

The government has proposed new regulations for social media platforms following growing concerns about online harm, such as child abuse, bullying, fake news and internet addiction.

The proposals, which are due to be published in a white paper later this year, would mean tech companies, such as Facebook and Google, were regulated in much the same way as the mobile phone and broadband industry.

This would have a particular focus on ensuring children are protected online and would reportedly include targets for removing offensive content within a specific time period or, failing that, the threat of hefty fines.

Who else has given evidence?

The committee has already heard from members of the Youth Select Committee, the National Children’s Bureau, Barnardo’s and Kidscape.

Dozens of children, parents, experts and other groups have also submitted written evidence giving their views on the main problems posed by social media and setting out what should be done to address them.