The UK's financial regulator has written to another batch of firms for information about any links they may have to the law firm at the centre of the Panama Papers saga.

The firms were required to send their initial findings to the FCA late last month after it gavethem until Friday 15 April to check for ties to Mossack Fonseca or to companies that it had formed or managed. Speaking to the UK's Treasury select committee last Monday, the FCA's acting chief executive, Tracey McDermott, said: “It’s far too early to give any views as to preliminary findings, and there’s nothing necessarily illegal about having offshore arrangements, it all depends on their purpose.”

When Labour MP Helen Goodman asked whether the existing information represented the “tip of the iceberg”, McDermott replied it was hard to know what the iceberg was.

“There have been reports of some serious issues of criminality and some things which may or may not be attractive, but also may or may not be criminal,” she said.

McDermott also confirmed that the International Consortium of Investigative Journalists has not released the original leaked papers.

The furore over the Panama Papers data leak has provoked a number of venerable figures to speak out in defence of legitimate confidentiality. Those that have recently come forward to support the argument include Stewart Fleming, the managing director of Abacus, a professional services firm operating in Malta and the Isle of Man, and Professor Philippe Braillard, a senior academic in Switzerland.