The government of Bahrain cannot guarantee the safety of Formula One teams and spectators at this Sunday's Bahrain Grand Prix as violence escalates in the Gulf kingdom, according to the British former police officer who is working on security at the track.

John Yates, the former assistant commissioner of the Metropolitan police who is employed by the Bahrain government to advise on police reform, told the Guardian: "People say can we guarantee security. Of course we can't guarantee security. I'd be a fool to sit here and say that.

"Is it possible there might be an incursion on the track? Of course there is. It's an open event. Can you stop some idiot running onto the track? There have been other incidents of track incursions."

Yates also said police would retaliate with live rounds if necessary: "The police will have all the options you would expect. If the opposition started firing live ammunition, the police would respond with live," he said, adding: "But I don't think that's likely."

The British policeman, known universally as "Yates of the Yard", went to Bahrain on a six-month contract four months ago. He led the cash-for-honours investigation, but resigned last year following criticism of the police investigation into the News of the World phone-hacking scandal.

"There will be protests over the weekend. But we want to make this a sporting event not a security event. The man who is heading the security said he wanted security to be felt but not seen. And I applaud that.

"I judge it more likely there will be protests on the route and protests around the villages. I just hope it's a good event and I hope it goes off without too much trouble."

Yates made his comments as protesters stepped up their activity with a demonstration in middle of he capital, Manama, which had to be broken up with stun grenades, and promises of 15 further demonstrations overnight, compared with seven on Tuesday night.

The controversial Bahrain Grand Prix has been foisted on the reluctant F1 teams only after they were give assurances that they would be safe following meetings in Shanghai last week with Bernie Ecclestone, the sport's commercial rights holder, and a statement from FIA, the governing body.

Formula One has refused to get involved in the political and moral row which has engulfed Bahrain and has concentrated purely on the security aspect. The sport will be dismayed by the comments from Yates, who also said the police needed their own human rights. "What some of the police are facing it's horrific. I saw four or five cops with life-changing injuries, faces taken off, ingested flames and lungs damaged. Where are their human rights? The cops have taken some heavy, heavy injuries."

Yates dismissed much of the reported violence as "malicious propaganda". He added: "There will be incidents when police have not acted appropriately. You saw that in a supermarket recently, and that's being investigated."

He also played down allegations that the police are making preemptive strikes in the villages surrounding the capital.

He said: "There's allegations that people are arrested and not taken to the police station but go to these holding sites where allegedly terrible things happen. But that would be on YouTube. That would be posted."

Following an independent inquiry into the bloodshed in Bahrain last year, Yates said that what happened in the country was "tragic" and "appalling".

He added on Wednesday: "But the will is there to move on and make the changes. I've seen a of changes in the four months I've been here. Some of the pace of the change is frustrating for some but it's the nature of the beast. But the will is there."