The former chairman of the Co-op Bank has been banned from the financial services industry by the Financial Conduct Authority (FCA).
Paul Flowers was chair of the bank between 2010 and 2013 but was forced to step down following allegations he bought and used illegal drugs, as well as claiming inappropriate expenses.
He was secretly filmed handing over £300 in cash for drugs in 2013 and admitted being in possession of cocaine, crystal meth and ketamine at Leeds Magistrates' Court in May 2014.
The FCA said on Tuesday that Mr Flowers' conduct demonstrated a "lack of fitness and propriety" required to work in financial services.
Mark Steward, executive director of enforcement and market oversight said: "The role of chair occupies a unique place of trust and influence. The chair is pivotal in setting expectations of a company's culture, values and behaviours.
The FCA found that Mr Flowers' actions proved he was unable to "meet the high standards of integrity and probity demanded by the role."
Its probe showed that Mr Flowers used his work mobile to make "a number of inappropriate telephone calls to a premium rate chat line", in breach of Co-op Group and Co-op Bank policies.
He also used his work email account to send "sexually explicit and otherwise inappropriate messages, and to discuss illegal drugs".
His 2014 court case heard that he had been a "cocaine user for the past 18 months" and "cited stress and the care of his terminally ill mother as reasons for his drug use".
After his arrest, he said he did not think he was qualified to run a bank and admitted that he had "sinned".
Then, in 2017, he was removed from the roll of church ministers, meaning he could no longer use the title reverend or lead services for "seriously impairing the mission, witness or integrity of the Church".