The GPs worked close to surgeries run by Shipman in Hyde, Greater Manchester.
It is alleged they failed to notice the doctor's unusually high death rates when counter-signing cremation forms.
Doctors Peter Bennett, Susan Booth, Jeremy Dirckze, Stephen Farrar, Alastair MacGillivray and Rajesh Patel all face charges of serious misconduct.
All the doctors, except Dr Booth, attended a GMC disciplinary hearing, which opened in Manchester on Monday.
They were criticised by Dame Janet Smith, chairman of the Shipman Inquiry, set up to investigate the doctor's 23-year killing spree.
Shipman was jailed for life in January 2000 for 15 counts of murder, but is now believed to have killed at least 200 further patients.
He was found hanged in his cell at Wakefield Prison in January.
The doctors counter-signed a total of 240 cremation forms for Shipman over 18 years - 124 of these patients were later ruled to have been unlawfully killed.
Lack of care
The hearing heard that the circumstances surrounding the death of many patients should have led to the involvement of a coroner, but instead, because the doctors had completed the necessary form, their bodies were released for cremation.
Nigel Grundy, for the GMC, said the doctors should have noted the "extraordinary coincidence" of the circumstances surrounding the deaths of Shipman's patients.
He said: "In each case we submit the alarm bells should have been ringing and they ought to have done something about it - either report it to the coroner, police or the GMC.
"At the very very least (they should have) reviewed the Form B of Dr Shipman's with particular care thereafter."
The doctors were based at the Clarendon House and Brooke practices, close to Shipman's Donneybrook and Market Street surgeries.
A seventh doctor, consultant pathologist Dr David Bee, 74, of Stockport, Cheshire, was last month found to have made mistakes in his post mortem examination of one of Shipman's patients.
These were not deemed to constitute serious professional misconduct. However, the Council for Healthcare Regulatory Excellence is currently reviewing that decision.
The doctors each deny a charge of serious professional misconduct.