FILE PHOTO: The logo of Deutsche bank is seen in Hong Kong, China July 8, 2019. File photo: REUTERS/TYRONE SIU
FILE PHOTO: The logo of Deutsche bank is seen in Hong Kong, China July 8, 2019. File photo: REUTERS/TYRONE SIU

For the umpteenth time, Deutsche Bank is ensnared in an alleged regulatory blunder. Except this time, the stakes are greater than its own integrity: confidence in its regulator, the European Central Bank (ECB), is on the line too.

The ECB is considering whether to probe Germany’s biggest bank for trading in its riskiest debt without the regulator’s approval, according to the German newspaper Sueddeutsche Zeitung.

In an effort to maintain liquidity in the bonds, the firm’s securities unit continued to make a market in the notes well after they were sold to investors. Typically, banks need to be authorised to buy their own subordinated bonds because they count as equity capital that should help a lender absorb potential losses.

By secretly buying the notes, Deutsche could have created a false market for the bonds, keeping a lid on its overall borrowing costs. That would also have left investors in the dark about how the bank’s capital might have been affected by the purchases. While it is not clear how much of the debt Deutsche had on its books at any one time, nor what effect the trades may have had on the bonds’ prices, the purchases allegedly went on for years.

What’s more, after being told by the ECB in 2014 that it should stop buying the bonds, Deutsche allegedly carried on doing it until 2017. Only then did it receive the regulator’s green light, and not retroactively.

Why the ECB, which assumed regulatory oversight of Europe’s biggest lenders in 2014, is digging into this only now is a mystery. It may turn out that Deutsche misunderstood the guidance it received from the ECB, or that the numbers involved were immaterial, which led the ECB to put off a formal probe. Or maybe Deutsche thought it was able to make a market in the notes under terms spelt out in the offer documents. Deutsche and the ECB declined to comment for this piece.

But the ECB is a young regulator and its record so far as an enforcer of the financial rule book is somewhat spotty. Setting the record straight on what is potentially a serious breach is not inconsequential.

The years in question were a period of turmoil for Deutsche. Faith in its ability to meet its obligations reached a nadir as clients worried whether the lender could afford a huge US fine for selling toxic mortgage securities. Customers were pulling billions of euros of cash every day. There were fears that the firm would run out of reserves to pay interest to bondholders, specifically on its subordinated, additional Tier 1 notes. Some notes fell to a low of 70c on the euro in February 2016

The ECB must show it is doing all it can to establish an account of what happened, not least because this is not the first time that its banking oversight has been called into question.

At the height of Deutsche’s troubles in 2016, the ECB let the lender include in its stress test results the proceeds of a sale that had not yet been completed, the Financial Times has reported. And earlier in 2019, Bloomberg uncovered how the ECB had signed off on Banca Monte dei Paschi di Siena SpA’s $6bn bailout even though it was aware the bank was probably insolvent.

It is possible that Deutsche acted in good faith. But if the ECB wants to build the trust of investors and depositors, it should eliminate any lingering doubts.

• Martinuzzi is a Bloomberg Opinion columnist covering finance and Ashworth is a Bloomberg Opinion columnist covering European markets. This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.