Postal ballots have still yet to be issued to the around 160,000 party members who will pick a successor to Boris Johnson, as a result of the GCHQ concerns. The ballots were due to be sent out from Monday, but members have now been warned they could arrive as late as Aug. 11, the report added.

(Reporting by Shivam Patel in Bengaluru and James Pearson; Editing by Chris Reese)