The former chief executive of ­Chelsea, once described as “the most powerful woman in football”, is ­facing ­questions about what she knew of secret payments made under the club’s former owner Roman ­Abramovich, amid a continuing investigation into alleged breaches of football spending rules.

Details of millions of pounds in fees, funded by offshore investment vehicles belonging to the Russian ­oligarch, emerged last year as a result of the Cyprus Confidential leaks ­project, published by the Guardian and international partners.

Documents from the files ­indicate that Marina Granovskaia, a close associate of Abramovich who ran Chelsea until he sold the club in May 2022, knew about some of the ­transactions, including a fee paid to the agent of star player Eden Hazard.

She also appears to have ­benefited personally from some of the ­payments, raising questions over whether she received extra money from Abramovich for her work at the club, on top of her Chelsea salary. The files suggest offshore companies in the Abramovich network made loans to Granovskaia worth £7.5m to finance the purchase of a house in Fulham, near the club’s Stamford Bridge stadium, and a payment of £1.63m for “financial, tax and legal due diligence”.

The Premier League is ­investigating whether ­Abramovich secretly subsidised his team by using offshore companies to make payments which should, under rules designed to ensure fair competition, have been made by the club itself from its own bank accounts.

The material raises questions about oversight of the club’s affairs by its board, which was chaired by the American lawyer Bruce Buck ­during Abramovich’s highly ­successful reign. Buck was a partner at the law firm Skadden, which acted for Chelsea and Abramovich for two decades, and held senior positions at the Premier League, which acts as both regulator and promoter for its member clubs.

The Premier League ­investigation was triggered after the club’s new owners, a consortium whose ­figurehead is the US investor Todd Boehly, reported suspected breaches by previous management. An ­independent panel of sports law experts will be convened that could summon former club ­executives to give evidence. Should the panel find Chelsea guilty, it has the power to impose financial or ­sporting ­punishments, such as a points deduction.

No details of the transactions under investigation have been publicly disclosed by the club, or the Premier League and Football Association.

However, a leak of documents from an accounting firm in Cyprus which acted for Abramovich revealed a series of payments over a decade to managers, scouts and football agents connected to Chelsea. The ­information, published as part of the Cyprus Confidential series, was shared with the Guardian by the International Consortium of ­Investigative Journalists (ICIJ) and Germany’s Paper Trail Media.

Beneficiaries of secret payments included the agent of Hazard, the files suggest, while other transactions appear to have been connected to the purchase of the Brazil forward Willian and the Cameroonstriker Samuel Eto’o.

Granovskaia appears to have been sent copies of agreements relating to those payments.

The Russian, 49, rose from ­working as Abramovich’s executive assistant to overseeing Chelsea’s financial and sporting affairs on the oligarch’s behalf, a job that saw her dubbed the “most powerful woman in football”.

Less than a month after she became chief executive of the club in October 2014, the ­British Virgin Islands-registered Ovington Worldwide – owned by ­Abramovich – agreed to make three loans to Granovskaia worth a ­combined £12.5m, documents in the leak reveal.

According to credit agreements, two of the loans, dated November 2014 and worth a combined £7.5m, were to finance the purchase of a property.

Less than six months later, Land Registry filings show, Granovskaia bought a home in London for £5.05m.

At least £7.5m of the debt to ­Abramovich was due to be waived under subsequent debt ­forgiveness deeds.

On top of the loans, between 2010 and 2019 Ovington Worldwide agreed to pay her at least £1.63m under an advisory services ­agreement for “financial, tax and legal due diligence”.

Leading sports lawyers have ­previously told the Guardian that any payment for services to Chelsea ought to have been borne by the club and that any failure to disclose them in the club’s accounts might be seen as a breach of Premier League rules.

The documents also suggest that Granovskaia may have known of ­payments made by one of ­Abramovich’s offshore vehicles to a football agent and an adviser, both of whom did business with Chelsea.

In April 2013, the Cyprus-based financial services firm MeritServus, which managed offshore companies for Roman Abramovich, wrote to Granovskaia at her postal address at Chelsea’s stadium.

MeritServus said it had enclosed a copy of an “advisory services ­agreement” with Gulf Value FZE, a company owned by John Bico, the former agent of Hazard. As the ­Guardian has previously revealed, the agreement involved Bico’s ­company receiving a £7m fee from ­Leiston Holdings, an offshore ­company owned by Abramovich.

A year earlier, MeritServus also sent Granovskaia a copy of an ­advisory agreement between Leiston and the former Dutch football coach Piet De Visser, who became one of Abramovich’s most trusted advisers during his ownership of Chelsea.

Under the ­agreement, Leiston agreed to pay De Visser a €48,000 “retainer” and a further €4,000 a month for “scouting and other ­football related advice”, over 12 months.

Granovskaia did not return requests for comment.

Chelsea’s free-spending strategy under Abramovich has long attracted concern within football, with the then Arsenal ­manager Arsène Wenger describing it as “financial doping” in 2005. The former Uefa president Michel Platini warned in 2008 that “the ones who cheat [with debt-fuelled spending] are going on to win”.

But the Premier League, which oversees top club’s finances, did not open an investigation into Chelsea until last year, after the club’s new owners reported that “incomplete financial information” had been ­submitted during Abramovich’s tenure.

In 2012, while Buck was chairman of Chelsea and the Premier League’s pay committee, he promised Chelsea would comply with Uefa’s “financial fair play” spending limits, imposed in 2011, via legitimate means.

These, he said, would include ­cutting ­spending and increasing sponsorship ­revenues. The following year, he criticised FFP rules, which he said risked maintaining the “status quo” in football. The Premier League imposed its own spending limits two years later.

Leaked files indicate that ­Skadden, the law firm where Buck was a ­partner, may have performed work for Leiston Holdings, the offshore vehicle owned by Abramovich that was the source of many of the ­payments likely to be investigated by the Premier League.

In a document that describes ­Leiston as the “customer” and ­Abramovich’s personal investment firm Millhouse as the “executor”, Skadden is listed among companies to have provided services requiring “transfer outside Russian federation” during 2014. Buck’s name does not appear in the document.

Lawyers for Buck did not return requests for comment. Skadden, Arps, Slate, Meagher & Flom did not return requests for comment.

Chelsea FC has previously said that the payments pre-date the current ownership regime and that the club had self-reported “potential financial irregularities” from that period to the football authorities.