An image used by police to illustrate slain Brazilian electrician Jean Charles de Menezes' physical resemblance to a terrorist was digitally altered, prosecutors said on Wednesday.

Menezes was shot by police, who mistook the 27-year-old for a suicide bomber, and prosecutors argue that a catalogue of police failures led to De Menezes' death and put the safety of the public in danger.

Police say they were acting during a period of extremely heightened insecurity and that it had been difficult to identify the Brazilian because he looked similar to terrorist Hussain Osman, whom they were hunting at the time.