Footage showed Mr Tomlinson being shoved by an officer - video courtesy Guardian.co.uk
The Metropolitan Police has denied trying to "cover up" the death of Ian Tomlinson during the G20 protests.
London's former mayor Ken Livingstone said officers colluded to hide the fact that Mr Tomlinson, 47, was attacked by police minutes before he died.
The Met said there was no intention to mislead following after the newsagent died of a heart attack on 1 April.
The Independent Police Complaints Commission (IPCC) has launched a criminal investigation into the matter.
The force only acknowledged Mr Tomlinson had "contact with police" before he died after video footage of the attack came to the public domain.
"To clarify, there has been no denial from the Met that this was the case, nor any deliberate intent to mislead," a spokesman said.
"This is information that could only have been known as the investigation progressed as this was not known at the time of providing medical aid to Mr Tomlinson."
Video footage appears to show Mr Tomlinson being hit with a baton and being pushed from behind to the floor.
Mr Livingstone said local police officers had tried to obscure the truth from the beginning.
"It's now quite clear that a lot of local officers were colluding in trying to cover this up, hide it no doubt from the commissioner Sir Paul Stephenson and the public," he said.
The officer thought to be shown on video pushing Mr Tomlinson to the ground is to be questioned by the IPCC.
The IPCC has ordered a second post-mortem test as part of its inquiry following the release of the video footage.