A minister apologised to parliament yesterday for telling MPs that 70 police officers were hurt during a climate change protest, after the Guardian revealed that most of the injuries were inflicted by insects or the heat. Vernon Coaker, the Home Office minister, told MPs at Commons question time yesterday: "I was informed that 70 police officers were hurt and naturally assumed that they had been hurt in direct contact as a result of the protest. That clearly wasn't the case and I apologise if that caused anybody to be misled."

The apology followed a freedom of information request from the Liberal Democrats, which showed that no officers in the £5.9m police operation at Kingsnorth power station in Kent during August had been injured by protesters.

Instead, police records showed that their medical unit had dealt mostly with toothache, diarrhoea, cut fingers and "possible bee stings".

David Howarth, the Lib Dem justice spokesman, asked Coaker to "revise his conclusion" that the policing was "proportionate and appropriate. Large numbers of protesters were injured at the hands of the police, especially by baton injuries," he said. Coaker said that he would be meeting representatives of the Association of Chief Police Officers to discuss the "lessons to be learned" from Kingsnorth, and the National Police Improvement Agency was carrying out an inquiry into the handling of the demonstration.

Labour's David Taylor said: "When people expressed concerns about the vigour and resources devoted by the police to the Kingsnorth climate camp, we were told that it was justified because there were dozens of injuries that occurred. Unless the protesters are to be held responsible for wasps and the weather, aren't we to conclude that the justification used at that time was wholly bogus and vacuous?"

A spokesman for the climate camp welcomed the apology but said that activists were not surprised that the FoI requests had revealed no violence.

"We are a completely peaceful movement. Yet for three years now we have been branded as a violent minority by the police and the government with no evidence whatever," said Nick Thorpe.

"At last the truth is coming out.

"They cannot keep getting away with criminalising us and repressing the very people who are trying to do something about climate change."

"We saw an utterly extraordinary blanket use of stop and search powers at the Kingsnorth climate camp in the summer, mass confiscation of everything from water pipes to marquees to crayons. Unarmed protesters were beaten to the ground by riot police in order to protect the profits of an energy corporation.

"There will be more protests and more direct action," he said.

Climate activists in Scotland yesterday blockaded the entrance to the Scottish Coal-operated Ravenstruther coal rail terminal in South Lanarkshire in protest against a growth in coal mining in Scotland.

The home secretary, Jacqui Smith, also apologised to MPs yesterday for last week's premature release of data on knife crime, which provoked fierce criticism from Sir Michael Scholar, chairman of the UK Statistics Agency. Scholar accused the government of "premature, irregular and selective" use of the statistics.

Smith told MPs: "I am sorry that I think we were too quick off the mark with the publication of one number in relation to the progress that had been made with tackling knife crime."