The sports scientist at the centre of the Essendon drug scandal, Stephen Dank, used an unfounded allegation about Collingwood using banned drugs to pressure coach James Hird to authorise the controversial peptide program, according to a key witness in the investigation.

Biochemist Shane Charter, who has spoken to ASADA several times, including in the past week, has explained that Dank asked him to verify that the Magpies had been using human growth hormone in order to persuade Hird to get the peptide program ''over the line''.

Charter, who sourced the peptides from China, said he flew to Queensland at Dank's request in December 2011 to help sell the program to Hird. He said he had never sold or supplied Collingwood with substances or had knowledge of its supplements program.

''Dank had been telling Hird that Collingwood was on human growth hormone and that we had to get the peptide program over the line,'' Charter told Fairfax Media in a previous interview. It is understood he has given the same information to ASADA, which is set to hand down its report on Essendon in the coming days.