Donald Trump has been banned from Facebook for two years.
The social media giant said that the former US president would be excluded from the site after a "severe violation" of its rules.
A statement released on Friday, signed by vice-president Nick Clegg, said the "gravity of circumstances" had led to the decision.
Mr Trump, 74, had been removed from Facebook in January after he praised violence in the US Capitol.
The ban was initially open-ended but has now been turned into a two-year fixed-term period, running from the start of the suspension until 2023.
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Mr Trump's account will be reviewed at the end of the ban if "the risk to public safety has receded", the statement added.
But further violations could lead to a permanent exclusion from Facebook, it warned.
The company also said it accepted that the decision would be "controversial" but wanted to be "proportionate, fair and transparent".
The statement said: "Last month, the Oversight Board upheld Facebook’s suspension of former US President Donald Trump’s Facebook and Instagram accounts following his praise for people engaged in violence at the Capitol on January 6.
"But in doing so, the board criticized the open-ended nature of the suspension, stating that 'it was not appropriate for Facebook to impose the indeterminate and standardless penalty of indefinite suspension'.
"The board instructed us to review the decision and respond in a way that is clear and proportionate, and made a number of recommendations on how to improve our policies and processes.
"We are today announcing new enforcement protocols to be applied in exceptional cases such as this, and we are confirming the time-bound penalty consistent with those protocols which we are applying to Mr. Trump’s accounts.
"Given the gravity of the circumstances that led to Mr. Trump’s suspension, we believe his actions constituted a severe violation of our rules which merit the highest penalty available under the new enforcement protocols.
"We are suspending his accounts for two years, effective from the date of the initial suspension on January 7 this year.
"At the end of this period, we will look to experts to assess whether the risk to public safety has receded.
"We will evaluate external factors, including instances of violence, restrictions on peaceful assembly and other markers of civil unrest.
"If we determine that there is still a serious risk to public safety, we will extend the restriction for a set period of time and continue to re-evaluate until that risk has receded.
"When the suspension is eventually lifted, there will be a strict set of rapidly escalating sanctions that will be triggered if Mr. Trump commits further violations in future, up to and including permanent removal of his pages and accounts.
"In establishing the two year sanction for severe violations, we considered the need for it to be long enough to allow a safe period of time after the acts of incitement, to be significant enough to be a deterrent to Mr. Trump and others from committing such severe violations in future, and to be proportionate to the gravity of the violation itself."
Mr Trump served as US president from 2017 to 2021.
He regularly used social media to fire off controversial statements, and has been reprimanded by Twitter.
His initial ban from Facebook - which also owns Instagram - came after he posted messages of support about rioters at the US Capitol in Washington, D.C.
A mob of his supporters stormed the meeting place of the United States Congress in protest over current president Joe Biden's election victory earlier this year.
Five people were killed either during or in the aftermath of the event, with more than 140 injured.
The scenes were widely condemned across the US and led to Mr Trump being impeached for the second time - a presidential record.
