A video on the newspaper’s website shows Flowers, a Methodist minister, in his car discussing buying cocaine and crystal meth, then counting out £300 in £20 notes.
The Mail on Sunday says it was handed a video and a series of text messages by an acquaintance of Flowers.
The newspaper says the text messages show Flowers was using drugs days after appearing before the Treasury select committee on 6 November, as part of the MPs’ inquiry into the collapse of the Co-op’s proposed deal to buy 632 Lloyds Banking Group branches.
Flowers was chairman of Co-op Bank from April 2010 until June this year. The bank has reported losses of £709m for the first half of the year, and agreed a revised rescue deal earlier this month to plug a £1.5bn capital shortfall. Earlier this month the Co-op Bank announced plans to cut its branch network by 15 per cent alongside a rescue deal which will see the Co-op Group’s stake in the bank reduced to 30 per cent.
In a statement released on The Methodist Church website, Flowers says: “This year has been incredibly difficult, with a death in the family and the pressures of my role with the Co-op Bank.
“At the lowest point in this terrible period, I did things that were stupid and wrong. I am sorry for this, and I am seeking professional help, and apologise to all I have hurt or failed by my actions.”