Security guard Gaby Hutchinson, 23, and Rebecca Ikumelo, 33, lost their lives when people forced their way into a concert by Nigerian artist Asake on 15 December.

The Security Industry Authority (SIA) is looking at allegations that some security staff regularly took bribes.

The claims were made in a BBC File on 4 programme in which one guard said "a couple of hundred" extra people would often be let in for cash and that some staff "made £1,000".

The source said it also happened on the night of the crush in south London and alleged that the company involved, AP Security, knew what had been going on.

Paul Fullwood, the SIA's director of inspections and enforcement, said his organisation was helping the police investigation.

"As the regulator of the private security industry in the UK, we take allegations of corruption by security operatives extremely seriously," he said.

"We have today launched an inquiry into these allegations which appear to extend beyond the Brixton O2 Academy.

"We will also review licensing arrangements and take appropriate action against any individual or company carrying out such practices as part of our regulatory licensing responsibility across the private security industry."

The O2 Academy in Brixton is one of London's most popular gig venues but on Wednesday its licence was suspended until at least 16 April as the investigation continues.

Police have opened an online portal where people can submit information, pictures and video.

A lawyer for the Metropolitan Police told Lambeth Council's licensing sub-committee how a crowd of about 1,000 people had gathered outside the venue, with some pushing against the doors and forcing them open.

Four people were admitted to hospital, said Gerald Gouriet KC.

"Tragically, as we know, two of them died as a result of their injuries. A third remains critically ill and the fourth has been, thankfully, discharged."

The music venue's lawyer, Stephen Walsh KC, said the O2 Academy offered "sincere condolences to the families of those who died during that tragic incident and its genuine concerns for anyone affected by it".

Sky News has contacted AP Security for comment.