Foreign Secretary Philip Hammond has described the UN working group's report on Julian Assange "ridiculous" and said the WikiLeaks founder is a "fugitive from justice".
The UN panel ruled Mr Assange is being "arbitrarily detained" in the Ecuadorian embassy in London and called for him to be paid compensation.
But Mr Hammond said the panel lacked credibility.
I reject the decision of this working group. It is a group made up of lay people and not lawyers. Julian Assange is a fugitive from justice. He is hiding from justice in the Ecuadorian embassy.
He can come out any time he chooses... But he will have to face justice in Sweden if he chooses to do so. This is frankly a ridiculous finding by the working group and we reject it.
A five-person panel became four before even looking at the Assange case and ended with the group divided and ridiculed by Philip Hammond.
From his 2010 arrest warrant to a UN expert panel's call for the WikiLeaks founder to be freed, review the key dates in the Assange case.
Read the full statement by the UN panel, calling for Julian Assange's "right to compensation" and for his "deprivation of liberty" to end.