Trade unions have been given new powers to expel people who have extreme political views from their memberships.
The BNP is widely accused of racism and xenophobia
It follows a number of cases where British National Party members took legal action against unions after they were expelled from membership.
Unions will be able to exclude those who contravene their rules on equality and diversity, the government says.
"We welcome the support the government has shown us on this issue," said TUC General Secretary Brendan Barber.
But the acting general secretary of the train drivers' union Aslef, Keith Norman, said he wanted tougher measures to exclude unwanted right wing members.
The Employment Relations Minister Gerry Sutcliffe said unions had been forced to pay large amounts of compensation to political extremists who peddled racist or xenophobic views.
The government now hopes the provision will take away the financial incentive for cases to be brought against unions.
A spokesman for the BNP opposed the measure, calling it an "outrage".