Dozens of delegates were left stuck outside the ICC in Birmingham as the Chancellor prepared to deliver his speech in the venue's main hall.
Birmingham Police tweeted: "Due to a potential security alert we have temporarily restricted access to and from the ICC."
Delegates were not allowed to enter or leave the building for around an hour and a half. It fully reopened shortly after 5pm.
Police tweeted: "Security restrictions at the ICC have been lifted following a potential security alert.
"Delegates and visitors are now able to leave the centre. We would like to thank everyone for their patience."
It comes after Tory Party chairman Jake Berry MP wrote to West Midlands Police and Crime Commissioner Simon Foster raising concerns over security at the conference.
A number of delegates, including Lichfield MP Michael Fabricant, say they have faced intimidation on their way into the venue where anti-Tory protesters have gathered.