Former Co-op Bank chairman Paul Flowers has spoken in detail for the first time about his treatment for drug addiction.

Mr Flowers was the £132,000-a-year chairman of the Co-op Bank from 2010 until May last year when he stepped down as the bank’s financial woes became apparent. The bank lost £700 million in the first six months of 2013.

In November last year, The Mail on Sunday published video showing Mr Flowers, who was also a Methodist minister, discussing a purchase of cocaine and crystal meth from a dealer in Leeds.

In the footage Mr Flowers counts out £300 in £20 notes.

Texts of Mr Flowers mentioning how his plans for a party were “turning into a two day, drug fuelled gay orgy!!!” were also published by the paper.

The revelations came three days after Mr Flowers had given a disastrous performance in front of the Treasury Select Committee regarding the bank’s ailing health.

Mr Flowers failed to identify the size of the Co-op’s balance sheet, he replied: “£3billion”, when the actual figure at the time was £47bn.

He also failed to answer questions about the amount of loans on its books.

Co-op Group chairman Len Wardle resigned as a result of the fallout.

Mr Flowers was then arrested and bailed in connection with a drugs supply investigation, described as “ongoing” by police.

He was also suspended indefinitely by the Methodist Church.

Further revelations showed Mr Flowers resigned as the trustee of a drugs charity in 2004 after allegedly lodging false expenses claims.

After his arrest, he underwent a 28-day addictions treatment programme before Christmas.

On Tuesday, he told BBC Newsnight: “I found that both cathartic and traumatic, but it actually helped me to look at not so much the superficial issues of the addictions themselves, but the more deep-seated reasons why people resort to any sort of addiction, and for me that was I think life-changing.

“I think I’m now much more secure in my own skin, much more self-aware certainly than I was before. I put that down to the treatment at the hospital and I continue to go there every week for therapy.”