ExxonMobil has sued the US Treasury in an attempt to stop a fine for allegations it behaved with “reckless disregard” for violating Russian sanctions while Rex Tillerson, now US secretary of state, was chief executive in 2014. The Treasury’s Office of Foreign Assets Control fined Exxon the maximum penalty of $2m in what it called an “egregious” case, saying it had failed to disclose breaches of sanctions over deals with Igor Sechin, chief executive of Russia’s state-controlled oil group Rosneft. Exxon responded with a lawsuit and an angry rejection of the Treasury’s allegations, describing Ofac’s action as “fundamentally unfair”. It accused Ofac of “trying to retroactively enforce a new interpretation of an executive order” inconsistent with guidance from the White House and Treasury. The lawsuit asks the court to deem the finding of sanctions violations “unlawful” and set it aside, as well as wipe away the $2m penalty. The oil group is seeking to permanently preventing Ofac from collecting further civil penalties related to the alleged offence. The dispute comes at a time of intense scrutiny of links between the US and Russia, prompted by allegations of Russian interference in last year’s election campaign to help Donald Trump become president. Ofac said on Thursday that presidents of Exxon’s US subsidiaries had violated sanctions by signing “eight legal documents related to oil and gas projects in Russia with Igor Sechin”, who had been designated as a sanctioned individual. It said the documents were signed in May 2014, a month after the sanctions on Mr Sechin and others were imposed.