Metropolitan police commanders at the G20 demonstrations ordered officers to clear the streets of protesters using "reasonable force" if necessary, minutes before a police constable attacked the newspaper vendor Ian Tomlinson, it emerged tonight.

Decisions taken by senior Met officers in the lead-up to Tomlinson's death were set out for the first time in an official report today into the policing operation at the protests in the City of London.

The report, by Denis O'Connor, the chief inspector of constabulary, found serious failings in the Met's policing operation and recommended a far-reaching overhaul of the way protests are policed in the future. Nationwide tactics for policing protests are outdated and inadequate, and pay insufficient regard to human rights obligations, it said.

The previously unseen police logs from 1 April include two tactical orders that shed light on events surrounding Tomlinson's death and more than 50 complaints made to the Independent Police Complaints Commission about alleged excessive force.

At 12.20pm, soon after the protests at the Bank of England had started, a Met Bronze commander, responsible for operational tactics on the ground, sowed confusion by ordering that police cordons placed around protesters in the so-called "kettle" should be "absolute cordons with discretion".

O'Connor's report described the instruction as "confusing and difficult to implement" for officers, who had to handle crowds that were far larger than senior officers had expected.

The report also revealed how senior officers met later in the day, after the most serious clashes had dissipated, to discuss how to manage a crowd that was assessed by police as "hostile, with continuing sporadic outbreaks of violence".

Senior officers decided that from 7pm "reasonable force would be used" to clear the streets of those who did not leave the area voluntarily. At 7.15pm, Tomlinson, who had been prevented from passing three police cordons as he tried to find a route home, was struck from behind and pushed to the ground by a Met officer who has since been suspended. His widow, Julia, said tonight that the commander's logs had made difficult reading. "They ordered that Ian could not leave and they ordered the use of force," she said. "If Ian is to get justice it means then all the officers who played a role in his death are made to account for what they did."

O'Connor stopped short of arguing that kettling should be abandoned. But he found commanders did not understand their legal duties when they decided to contain thousands of protesters at the Bank of England and the Climate Camp, in nearby Bishopsgate.

Warning of the consequences if senior officers ignored his advice, O'Connor said there could be more disruption on the streets, police forces challenged in court and a withdrawal of the public's consent to policing.

Sir Hugh Orde, the incoming president of the Association of Chief Police Officers, said the problems encountered by the Met might not have arisen if human rights had been put at the centre of operational decisions.

The Met accepted the recommendations and launched an urgent review of training and tactics at protests.