Hillsborough match commander David Duckenfield has accepted his failure to close the tunnel was the direct cause of the death of 96 people in April 1989.
Giving evidence during the new inquest into the disaster, Mr Duckenfield said it had been the most difficult period of his life to admit his professional failing led to the deaths.
The police chief in charge of crowd control on the day of the Hillsborough disaster has admitted lying to former FA chief executive Graham Kelly about the opening of the gate at the ground and apologised unreservedly to the victims' families.
The jury in the inquest into the 1989 disaster earlier heard evidence from Kelly, who said match commander David Duckenfield told him the gate to the ground had been forced by Liverpool FC fans.
Today giving evidence at the inquest, Duckenfield admitted he had lied to Kelly.
Christina Lambert, counsel to the inquests, asked Duckenfield: "Do you consider now that you told Graham Kelly and others something that was not true?"
"Yes ma'am", he replied.
"Do you consider that you told them a lie?", she continued.
"Yes ma'am", Duckenfield replied.
He added: "That was a terrible lie. Everyone knew the truth. The fans knew we opened the gates. The officers knew we opened the gates."
Hillsborough match commander accepts his failure to close the tunnel was the direct cause of the death of 96 people in April 1989.
The police match commander at Hillsborough has said he thinks there was no conspiracy about the disaster.