Sajid Javid has hit out at Tory governments for "taking too long" to clean up the internet - despite repeated promises.
The ex-Cabinet minister said "nothing" had been done to make the web safer amid multiple delays to a long-awaited law.
As Culture Secretary Mr Javid published proposals to force online giants to take responsibility in 2018, but he added: "Four years later, nothing has happened".
The landmark Online Harms Bill proposes to introduce new requirements on social media firms to protect children from harmful and illegal content.
Companies that fail to do so could face fines of up to 10% of their annual turnover.
The Bill was due to go through the final amendments stage in the Commons before the summer recess - but was delayed at the last minute.
After entering No10 in September, Liz Truss also suggested the legislation - championed by former Culture Secretary Nadine Dorries - would be re-drafted.
She told MPs: "What I want to make sure is we protect under 18s from harm, but we also make sure free speech is allowed, so there may be some tweaks required."
Appearing on BBC Radio 4's Today programe on Mental Health Awareness Day, Mr Javid said: "It is an offence under the current suicide act to encourage or incite someone to kill themselves. But there's a huge gap when it comes to covering digital communication.
"We were all reminded of that just last week with the coroner's report into the tragic death of Molly Russell - you had Ian Russell on your programme, who talked about it so powerfully - and so that needs to happen, but the Government's taking too long.
"When I was home secretary, alongside Jeremy Wright the culture secretary, we introduced the white paper on online harm, and here we are, four years later, nothing has happened.
"Other countries have done this and nothing has happened. Four years."
In response to Mr Javid’s comments, the Prime Minister’s spokesman said: “This is an important issue and we want to get it right.
“Under the bill, tech platforms on all sides will have to identify and remove illegal content which promotes or assists suicide and additionally all sites likely to be accessed by children will need to be will need to prevent children from accessing harmful content and that includes self harm.
“On a new offence, we've agreed in principle to create a new offence and we're asking the Law Commission to advise on how this can be incorporated into criminal law.
“I recognise that process does take time. We want it to be done as soon as possible, but it's important to get that right.”
