British tax authorities are heading for a showdown with the media groups behind the Panama Papers exposé, demanding they hand over the cache of documents.

The Government has pledged £10million for a task-force to investigate the Panama data, but it is understood the authorities have so far only managed to get hold of some of the 11.5million documents.

Revenue & Customs told The Mail on Sunday it was ‘determined’ to get hold of the leaked information to pursue criminal investigations against tax fraudsters and would ‘explore every avenue, nationally and internationally’.

Demand: Revenue & Customs told The Mail on Sunday it was ‘determined’ to get hold of the leaked information

It said: ‘While we appreciate that the media is not an arm of law enforcement, given the seriousness of the allegations that they have published and the calls they have made for action to be taken, we would reasonably expect them to co-operate in giving us access to the Panama data.’

The documents were leaked from Panamanian law firm Mossack Fonseca to organisations including The Guardian and the BBC, leading to headlines around the world alleging widespread tax evasion and to calls for a crackdown.

Tax authorities from 35 of the richest nations met last week to discuss how to get hold of the Panama leaks and to manage the sharing and exploitation of the database. Sources suggested that they had already obtained part of the database, but not all of it.

Guardian News and Media and the BBC both argue they have only electronic access to the papers. GNM suggested Revenue & Customs should ‘contact the UK office of Mossack Fonseca directly’.

The German newspaper Suddeutsche Zeitung, which was leaked the data, and the International Consortium of Investigative Journalists, which coordinated the newspapers’ investigation, have said categorically that they will not hand it over.

If the data was held in the UK, Revenue & Customs could obtain it through a court order. Lawyers said German and US tax authorities may also be able to take similar action.