The law firm at the centre of the Panana Papers has threatened to take legal action against the International Consortium of Investigative Journalists over its release this week of leaked files.

Last month stories began emerging based on 11m leaked documents from the law firm Mossack Fonseca detailing the secret offshore business dealings of rich and powerful figures around the world.

These documents were shared with partner news organisations, including the BBC and The Guardian.

On Monday night the ICIJ made public a database of 360,000 individuals and companies involved in offshore structures.

In response, Mossack Fonseca has sent a “cease and desist” letter to the ICIJ, a precursor to possible legal action.

The law firm said in a statement: “Mossack Fonseca & Co. wants to communicate the latest action taken by the group in the light of the information breach it was victim of.

“Due to the way in which the media has fed from the information stolen from our system in order to disseminate out of context news and affect our reputation, we have been forced to take stronger actions.

“Today we sent a cease and desist letter to the International Consortium of Investigative Journalists (ICIJ) regarding its announcement to make public, on May 9 the second portion of the database stolen from our company.

“The letter urges the ICIJ to abstain from this action taking into consideration that it is based on the theft of confidential information and is a violation of the confidentiality agreement between attorney and client, which we must protect.

“It is important for us to make clear that we operate, in all jurisdictions, under strict compliance with the law and regulations of the industry in all services provided, respecting strong client identification norms.

“It is not common for our group to take these kinds of actions with media groups and we hope the polemic will not drag us into future legal actions. Our company is loyal to and promotes the freedom of the press, but we consider that practices like the one taken by the ICIJ does not align with the right to communicate the truth, without speculation and in a balanced way that respects and takes into consideration the right s of all other parties involved. ”

The company has responded to widespread reports that it has facilitated illegal practics by setting out details responses and statements on a website: mossfonmedia.com.

Last week the still-anonymous source behind the data leak broke their silence in a statement to the ICIJ.

They said: “Income inequality is one of the defining issues of our time. It affects all of us, the world over. The debate over its sudden acceleration has raged for years, with politicians, academics and activists alike helpless to stop its steady growth despite countless speeches, statistical analyses, a few meagre protests, and the occasional documentary. Still, questions remain: why? And why now?

“The Panama Papers provide a compelling answer to these questions: massive, pervasive corruption. And it’s not a coincidence that the answer comes from a law firm. More than just a cog in the machine of ‘wealth management’, Mossack Fonseca used its influence to write and bend laws worldwide to favour the interests of criminals over a period of decades.”