London's police chief Sir Ian Blair considered resigning after his force shot dead an innocent Brazilian they mistook for a suicide bomber.
Sir Ian said the "big job" is the fight against terrorism
He told the BBC's Hardtalk show that police should have scotched rumours Jean Charles de Menezes was wearing a heavy jacket and vaulted the barrier.
But he decided it was better to stay to help defend Britain from terrorism.
Asked if he would resign if criticised by the inquiry, he said that would depend "on the level of condemnation".
Mr Menezes' family called for him to quit over the handling of the shooting.
They said he should resign for wrongly linking the shooting to the attempted bombings of 21 July early on.
The 27-year-old electrician was shot by police at Stockwell tube station on 22 July - the day after several failed bomb attempts - when he was mistaken for one of the bombing suspects.
Sir Ian told Hardtalk's Stephen Sackur he "certainly" considered resigning.
Mr Menezes was shot a day after the failed London bombings
"In the sense of this...somebody makes those comments, you're not just going to brush it off," he said.
"No one in their right mind would be arrogant enough to rule it out."
However, he told Mr Sackur he did not come "very close at all" to quitting "because the big job is to defend this country against terrorism and that's what I'm here to do".
He added it would not have been right for the force, the country or the city of London for him to resign.
Sir Ian apologised to Mr Menezes' family over the death - an apology they have rejected.
The Independent Police Complaints Commission is continuing to investigate the incident.
Asked about police tactics in dealing with terror suspects, he said officers would have three options: to isolate suspects and shoot them from a distance; to isolate them so that their bomb blows up without injuring anyone else; or to shoot them at a close distance.
"The policy is for dealing with deadly and determined terrorists," he said.
He continued: "We have never had a debate about tactics. Now we need it. The public are entitled to a debate."
Sir Ian Blair appeared on Hardtalk's at 2330 BST on Wednesday 21 September on BBC News 24.