Berenberg's managing partner, Hans-Walther Peters, has refused to be questioned by members of parliament's committee of inquiry into money laundering, tax avoidance and tax evasion (PANA).
GUE/NGL group deputy Fabio De Masi, a Vice-Chair of the committee, said, "Peters has referred us to the 'ongoing investigations.'
"His no-show can only be interpreted as a guilty plea as Peters had already been invited to come before the Parliament in his role as acting president of the Association of German Banks.
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"But again, he ducked the invitation by sending over the general manager of the Association instead."
The German added, "The big German banks need to think twice about whether someone who may have a case to defend before a judge and one who shirks his public duties should be their choice as president of the guild."
He said, "Meanwhile, the European Parliament should be given the power to question under oath as soon as possible."
His attack on Peters comes as the cross-party committee continued its work on Thursday by quizzing two former compliance officers with Barenberg.
Both had been fired by the Hamburg-based bank for voicing concerns about their former employer's clientele.
De Masi told the hearing, "Drug trafficking, arms trade, money laundering, tax evasion, corruption, gambling - what criminal activities has Berenberg not been involved in? Some of the money in the Siemens slush fund scandal, for example, was wired through the bank.
"I'm delighted that both compliance officers - fired by Berenberg for warning about the company's dodgy clients - agreed to attend the committee hearing to provide their testimony."
Their agreeing to be questioned contrasts with Peter's no show, he said.
He said Berenberg had an excellent relationship with the now infamous law firm at the centre of the Panama Papers affair, Mossack Fonseca.
"The latter even praised the bank for quick and easy ways to set up accounts for letterbox companies. Ramón Fonseca, co-founder of the law firm, had several private accounts with Berenberg and one of the directors of Berenberg-Switzerland used one of the shell companies of the Panamanian law firm," said De Masi.
"One of Ramón Fonseca's sons even had a short-term internship at the bank. All of this shows Berenberg knew very well with whom they were dealing with. The bank therefore cannot profess ignorance over such serious matters", he said.
Other speakers at Thursday's hearing, which looked at the role played by lawyers, bankers and accountants in the scandal, were Benedikt Strunz and Soren Kristensen of the International Consortium of Investigative Journalists.
Meanwhile, a delegation from the committee travelled to the UK on Thursday in the first of a quartet of fact-finding missions to learn more about tax havens.
Future visits already planned include Malta, Luxembourg and the US.
Speaking ahead of the trip, De Masi, who was Parliament representative at the UK public accounts committee's global tax transparency summit in December, said, "The UK is at the heart of the world's largest web of tax havens and is intricately connected with the world of offshore finance.
"The Panama Papers showed that in no other European country are intermediaries more active than in the UK. Bermuda, Cayman Islands, British Virgin Islands - a list of who's who of global tax havens are thriving under the auspices of Her Majesty's government.
"And it's not just money laundering and tax: Europol's cross-examination of the Panama Papers with their counter-terrorism finances database flagged up the UK financial system as having one of the biggest concentration of suspects with more than 3500 hits," the MEP added.
"Tax dodging is not a petty crime and it ravages our budgets. The UK is also undermining our work on the EU's tax haven blacklist by preventing strong criteria for screening. Its government has already announced its intention to go further down that route post-Brexit and lower tax rates to a minimum."
On Thursday, Peters was not immediately available for comment.