on Friday designated all of an "Islamist terrorist group", warning that its members and those who support the group could face stiff jail terms.
, the military wing of the group that rules the has been banned in Britain since 2001 but the interior ministry extended the ban to its political entities.
London said last week it was no longer possible to make a distinction, assessing that "commits, participates in, prepares for and promotes and encourages terrorism".
"The Islamist terrorist group Hamas has today become a proscribed terrorist organisation in the UK in its entirety following parliament's approval," the Home Office said.
"This means that members of Hamas or those who invite support for the group could be jailed for up to 14 years."
Israel has welcomed the move, which follows similar action by the United States and the European Union.
But Hamas itself has called the UK move "a crime against our Palestinian people and all their history of struggle".