The younger brother of the Manchester bomber was a member of a jihadist cell believed to have been planning an attack on the UN’s special envoy to Libya, the Telegraph understands.

The plot to target Martin Kobler, the head of the United Nations Support Mission in Libya, during a visit to the capital Tripoli earlier this year was interrupted before it could be carried out, diplomatic sources said.

Libyan security services had been monitoring the group for months and claim they found Hashim Abedi, the 20-year-old brother of suicide bomber Salman, 22, to be a “significant player”.

They were apparently in the late stages of building an explosive device and intended to hit German national Mr Kobler's convoy.