Brennan is serving a two-year worldwide ban
Former Harlequins physio Steph Brennan has resigned from his role with England over his involvement in the fake blood substitution of Tom Williams.
Brennan, who joined the England set-up earlier this summer, had already been suspended by the Rugby Football Union.
He has been banned for two years from all worldwide competitions by the International Rugby Board after an admission of guilt over the incident.
Williams faked injury to allow fly-half Nick Evans to return to the field.
In a statement, the RFU said: "Mr Brennan wholeheartedly wants to apologise for any aspects of his behaviour that caused concern for the RFU and the physiotherapist profession."
Evans had departed injured in the 47th minute of the 6-5 Heineken Cup defeat by Leinster on 12 April before his replacement at number 10, Chris Malone, also went off injured later in the second half.
With time running out, Williams was seen with what appeared to be blood coming out of his mouth, which meant he could go off to be replaced by specialist kicker Evans.
Ex-Harlequins director of rugby Dean Richards has been banned from coaching for three years for his role in the fake blood injury.
Winger Williams's initial 12-month ban was reduced to four months on appeal.