Petrochemical Commercial Company (PCC), which is linked to the Iranian state, used a web of front companies in the UK to discreetly move money around the world, according to documents seen by the Financial Times (FT).
Lloyds and Santander UK provided bank accounts to two of those companies, the report revealed.
PCC UK has been subject to US economic sanctions since 2018. Sanctions, which can include the restriction of exports, are a tactic employed by governments to stop other countries acting aggressively or breaking international law.
PCC UK has links to Aria Associates, a company registered to a residential address on the banks of the Thames in central London.
Documents first reported by the FT and also seen by the PA news agency suggest Aria Associates had a bank account with Lloyds.
Aria Associates is not itself subject to sanctions and PCC UK is not sanctioned by the UK Government.
The business is majority-owned by Mohammad Ali Rejal, Companies House filings show.
Mr Rejal has held a senior position at PCC UK and has had communications with company officials in Iran, in emails reported by the FT and also seen by the PA news agency.
Meanwhile, Pisco UK is a company registered in Surrey which documents suggest had a Santander bank account.
The company is majority-owned by British national Abdollah Siavash Fahimi, who the FT reported is running the company on behalf of PCC.
The FT reported that Pisco UK and Aria Associates are fully owned by PCC UK, although the PA news agency was not able to independently confirm this.
A spokeswoman for Santander UK said the bank is “not in breach of US sanctions based on our investigation”.
“We have policies and procedures in place to ensure we comply with sanctions requirements and will continue to engage proactively with relevant UK and US authorities.”
Lloyds also said it has not breached any sanctions, with a spokeswoman saying: “The group’s business activities are conducted to ensure compliance with applicable sanctions laws.
“We are committed to adhering to all legislative and regulatory requirements as they relate to economic crime. We are not permitted to comment on individual customers.
“In addition, due to legal restrictions, we cannot comment on the submission of suspicious activity reports to relevant authorities when and if they occur.”
Shares in Madrid-listed Banco Santander were down more than 4% on Monday and FTSE 100-listed Lloyds shares were down about 1%.