Metropolitan Police Commissioner Sir Mark Rowley has said he “wouldn't be surprised if more people came forward” about Russell Brand after his rape conviction, as officers continue two separate rape investigations into the entertainer.

Brand, 51, was convicted at Southwark Crown Court on Thursday of one count of rape and three counts of sexual assault. He was acquitted of two further rape charges and one allegation of attempted indecent assault. Refused bail, he remains in custody before sentencing on Monday. Mr Justice Bennathan told him to expect “a significant custodial term”.

The further investigations concern allegations by two women. Brand has denied those allegations and has already been interviewed under caution. Pre-trial legal documents suggest one woman was 16 at the time. None of the women featured in the media investigation were complainants in the criminal trial, which heard allegations from six women spanning 1999 to 2009.

Speaking on Friday, Sir Mark praised the women’s bravery and said most sexual offending involved people abusing power. He also challenged the treatment of complainants in court.

Asked about the defence barrister’s argument that none had “resisted, screamed or even tried to leave”, Sir Mark said reporting he had heard came “very close to victim blaming”. He strongly supported the Victims’ Commissioner’s call for a duty in the Courts and Tribunals Bill requiring judges to direct juries on rape myths in every rape trial. His objection was to suggestions that a victim’s failure to behave in a particular way undermined their case.

Brand’s lawyers had unsuccessfully sought to have the case dismissed at an October pre-trial hearing, arguing that publicity following the Channel 4 Dispatches programme prevented a fair trial.

The verdicts have also prompted scrutiny of Brand’s former associates. Prime Minister Andy Burnham said he had not known the extent of Brand’s conduct, describing his crimes as horrific. Labour figures had courted Brand before the police investigation; Ed Miliband interviewed him before the 2015 election. Burnham’s supportive 2014 tweet followed coverage of Brand’s housing arrangements, although its precise reference remains unclear.

Various Artists Ltd has asked its head of comedy, Jack Bayles, to step back while it considers the verdicts. A victim said Bayles and another employee pressured her to massage Brand before a 2009 sexual assault. Her manager’s statement recounted her account that the men laughed during it.

Bayles said he did not remember the incident, had co-operated fully with investigators and sincerely apologised for missing signs of distress. He described a toxic working environment, said no complaints were made to him and said he stopped working with Brand in 2010, with no contact since.