Lib Dem leader and former Business Secretary Sir Vince Cable has called on the Home Office and National Crime Agency to explain themselves over the revelation that the UK’s most important anti-money laundering agency let JP Morgan transfer $875m to a convicted money launderer involved in the notoriously “corrupt” Nigerian oil deal OPL 245.

On Thursday, we reported that JP Morgan’s London branch claimed it repeatedly sought consent from the Serious Organised Crime Agency (Soca) to pay Chief Dan Etete, a former Nigerian oil minister who was also a convicted money launderer.

But instead of being told to block the transfers, the bank says it was given the green light by Soca to proceed.

The details were contained in the US bank’s defence filed last week at the High Court against an $875m damages claim by the Federal Republic of Nigeria.

Why that permission was granted has not been explained, but campaigners say the decision means there is “real cause for concern” about the UK’s current anti-money laundering regime.

Reacting to our exclusive, Sir Vince, who was Business Secretary at the time of the transfers in 2011 and 2013, said: “I am shocked. This suggests serious weakness either in the UK’s anti-money laundering regime due to a lack of commitment or negligence.”

The Lib Dem leader added he will demand answers from the Home Office and the NCA.

The payments – to a front company controlled by Nigeria’s former oil minister Chief Dan Etete – were the proceeds from what is alleged to be one of the world’s most corrupt oil deals.

As oil minister in 1998, Etete had awarded a massive untapped oil block off the coast of Nigeria known as OPL 245 to a company called Malabu, in which he secretly held a major stake.

After leaving government and following several years of legal disputes, Etete decided to reject overtures from Russia and China and eventually sold the block to Shell and Italian oil company Eni in 2011 for $1.1bn.

The deal also involved the former Nigerian government of Goodluck Jonathan which agreed to act as a middleman. This meant Shell and Eni were not contracting directly with Etete.

At the time of the deal, Shell and Eni knew not only that Etete controlled Malabu, but also that he had been convicted on an unrelated money laundering case in Paris in 2007.

JP Morgan in its court defence argues it has done nothing wrong. It made three payments to Malabu over two years: two worth more than $800m in August 2011 and another of some $75m in August 2013. It says in each case the payment instructions from its client, the Federal Government of Nigeria, were lawful and valid.

DOWNLOAD JP MORGAN’S CORT DEFENCE HERE.

And it added that for every payment it had complied with the UK’s anti-money laundering laws by raising Suspicious Activity Reports with Soca. These reports would have been sent to the UK Financial Intelligence Unit within Soca, an arm that later transferred directly to the new National Crime Agency (NCA).

We asked the NCA why huge sums were allowed to pass to a convicted money launderer.

While refusing to comment on “individual cases of litigation”, it said that the transaction predated the NCA’s existence.

The NCA added: “Under the Proceeds of Crime Act 2002 (POCA) a reporting organisation which has received a defence from the NCA, or formerly SOCA, under POCA for a transaction has a defence against money laundering charges in a court. This is commonly known as the consent regime.

“Responsibility for undertaking the transaction or activity, or not undertaking it, remains with the reporting organisation.”

The Home Office is considering a series of questions posed by Finance Uncovered at the time of publication.

It is alleged that the money from the OPL245 deal was used to buy a private jet and armoured Cadillacs in the US, fine art and luxury shotguns in London, and to pay a series of kickbacks to various officials.

Shell, Eni and a number of their former executives are due to stand trial in Italy in May on corruption charges related to the deal. All parties deny any wrongdoing.

Goodluck Jonathan and Etete have also denied any wrongdoing.