Home Secretary Shabana Mahmood confirmed the suspect was not known to the government's anti-terrorism programme in an update to MPs.
The MP for Makerfield is on track to become the prime minister next week after receiving the support of the vast majority of Labour MPs.
Shabana Mahmood will use new powers to ban support for the group, which has been linked to death threats and intimidation on British soil.
Home Secretary Shabana Mahmood says the police's response "undoubtedly saved lives".
The UK signs a new services deal with Switzerland it says will increase exports by £5.2bn annually "in the long run".