Priti Patel made the decision on Friday, although Assange’s legal team will mount an appeal.
Former White House adviser Steve Bannon and rapper Lil Wayne are among those being granted clemency by the outgoing US president.
This week saw Assange dodge extradition to the United States.
The US has said it will appeal the decision.
Julian Assange Fathered Two Children Inside Ecuadorian Embassy Confirms Partner During Plea For His Release
Supporters of the WikiLeaks founder claim coronavirus is spreading through Belmarsh prison, where Assange is being held.
The WikiLeaks founder is no longer being pursued over rape allegations, but could still be extradited to the US. Here's what's happened so far, and why it's so controversial.
We do not get to pick our figureheads, and it’s in cases exactly like this that our freedoms are challenged, journalist James Ball writes.
The US "are demonstrating an extraordinary amount of hypocrisy" with their Assange extradition bid, said a spokesperson for Dunn's family.
Corbyn and McDonnell’s approach may not be shared by their successors.
WikiLeaks founder's lawyer claims Assange was asked to say Russia was not involved in the leak of Democratic National Committee emails.