Yang did not say how long Gao was sentenced to prison or where the prison was located. It was not clear whether Yang was referring to a charge of subversion brought against Gao in 2006 or new charges not made known to the public, the BBC reported.
Yang denied reports from international rights groups that Gao had been tortured.
Milliband had raised Gao's case with the Chinese government, which was willing to discuss it if Britain respected China's judicial system, Yang said
"We are willing to have human rights dialogue ... on the basis of mutual respect and non-interference in each other's internal affairs," Yang said.