Dimon under pressure as key lieutenant leaves

Pressure mounted yesterday on Jamie Dimon, the chief executive of JP Morgan, the investment bank which last week revealed a $2bn (£1.2bn) trading loss through its London office.

There are calls for him to resign his board membership on New York's central bank. Senator Bob Corker has also called for a full senatorial hearing into the JP Morgan losses.

Mr Dimon is set to face shareholders' anger at the Wall Street bank's annual meeting in Tampa, Florida today. Over the weekend, Mr Dimon admitted on American television that he had been wrong to describe the massive positions built up by the so-called London whale at the bank's chief investment office as a "tempest in a teapot". He said the losses could grow by another $1bn as the trades are unwound.

JPMorgan's chief investment officer, Ina Drew, one of Mr Dimon's closest lieutenants, left yesterday and other senior executives – including the London whale, Bruno Iksil – are expected to follow. It is widely reported that Mr Dimon encouraged Ms Drew's team to take larger and larger positions.

Mr Dimon – a fierce critic of greater banking regulation – is now in the firing line because JPMorgan appears to have broken its mantra of keeping risk as low as possible. He was embarrassed at the weekend when the New York Times published details of remarks he made at a dinner party when he called regulators infantile. There has also been a call for him to resign from the board of the Federal Reserve Bank of New York by Elizabeth Warren, who headed the congressional committee which oversaw the US bank bail-out and is currently standing for senate.

"Mr Dimon should resign from his post at the New York Fed to show that Wall Street bankers understand the need for responsibility and accountability," Ms Warren said. "We need to stop the cycle of bankers taking on risky activities, getting bailed out by the taxpayers, then using their army of lobbyists to water down regulations."