A British businessman who represents a Ukrainian oligarch is paying tens of thousands of pounds in donations to the Tories, the Guardian can disclose. Payments made by the businessman's company have caused concern to the Electoral Commission, which queried some of the donations earlier this year.

Pauline Neville-Jones, shadow security minister, former chair of the joint intelligence committee and a key Cameron foreign policy adviser, currently has her office sponsored by Robert Shetler-Jones, a close associate of the foreign billionaire Dmitry Firtash.

A company linked to Shetler-Jones is also making payments to Conservative central office. It is called Scythian Ltd. Shetler-Jones chairs and part owns it.

So far, more than £70,000 has been paid in total.

Under current laws and rules the arrangement is legitimate: the money is coming from a British individual and a UK-based company. But the Electoral Commission wrote to the Conservative party in July, querying the status of Scythian Ltd. The company had apparently always been dormant and was overdue with its accounts. Donations are only permissible under the rules if they come from a company that is genuinely "carrying on a business" in the UK.

The Conservatives obtained a letter from a Scythian Ltd auditor, they say, claiming the company was no longer dormant. But its accounts, which are a year overdue, have still not appeared on the Companies House register. The most recent Scythian declaration to Companies House, made only last month, described it as a "non-trading company".

The commission said last night it had been satisfied by Tory reassurances at the time, but were keeping the situation "under review".

A Conservative party spokesman said: "These donations have been declared to the Electoral Commission and are entirely permissible under the rules. The party has received confirmation that this company is carrying on business in the UK and the Electoral Commission has written to us stating they have no issues. All of our donations are declared to the Electoral Commission and we always adhere to the rules rigidly."

Shetler-Jones said yesterday: "All donations have come from me personally or from my UK company, Scythian Ltd, of which I am a shareholder. These donations reflect my personal support for the Conservative party and were not made in consultation with Dmitry Firtash or at his request." Shelter-Jones confirmed last night the company works for Firtash and his Group DF companies. He said: "Group DF is a client of Scythian Ltd. Our staff provide strategic, financial and management support for the Group and for Dmitry Firtash." He denied the company had no trading existence. "Scythian is not a dormant company. It has been trading for at least two and a half years," he said.

Scythian's premises are located in Mayfair. On the door of No 25 Knightsbridge, a palatial office block close to the Harvey Nichols store, Scythian is the only occupant listed.

The only entries on the official Companies House register for Scythian show that it has so far always been "dormant", has only £2 nominal capital, has never so far traded and is a year overdue with its accounts.

The same first floor at No 25 is listed on company records as simultaneously occupied by the DF Foundation. This is part of the Firtash group, according to the group's website, which also says Shetler-Jones represents the foundation. The charity began to fund Ukrainian language courses at Cambridge in February 2007.

A third listed phone number at the same first-floor address is the recently-founded British-Ukrainian Society, of which Shetler-Jones is also a director.

Like other Russian and Ukrainian oligarchs, Firtash is a fabulously wealthy man whose business dealings have been controversial. A former meat trader and secondhand car dealer, he made his fortune from trading with the energy-rich state of Turkmenistan, supplying food and other goods in exchange for gas that was then sold to Ukraine.

He came to prominence in 2006, when he was revealed as one of the men behind a company that controls Gazprom gas supplies from Russia to Europe, via Ukraine.

Yulia Tymoshenko, then prime minister of Ukraine, had alleged that the firm, RosUkrEnergo, was overcharging the country and had links to organised crime. There were allegations that Firtash had links with Semyon Mogilevich, an alleged mafia chief who had been arrested in Moscow, but the claims were strongly denied in statements issued on behalf of Firtash by Shetler-Jones.

Shetler-Jones heads the Firtash group of companies as their chief executive, and is also listed as being on the board of RosUkrEnergo.

Some of the Shetler-Jones donations are coming in as a £5,000 quarterly donation to Neville-Jones's office expenses. She declares it as money from him, provided through Conservative campaign headquarters. Another £30,000 has come in as individual donations from Shetler-Jones to Conservative central office.

Tymoshenko told the BBC in 2006: "We provided the president of the Ukraine with documented proof that some powerful criminal structures are behind the RosUkrEnergo company."

Firtash then emerged and declared himself to be the previously hidden part-owner of RosUkrEnergo. In the same Panorama programme, Shetler-Jones gave an interview as Firtash's "British representative". Asked about another company, in which Firtash's shareholding was hidden behind a trustee, he said: "Mr Firtash at that time did not want to be a public figure." But he said Firtash was not acting as a front for mafia bosses. "Given how close I am to him and his business, I would know," he said.

Denis McShane, a former minister for Europe, last night called for the Electoral Commission to examine the Shetler-Jones donations. He said: "The Electoral Commission now has a duty to start asking serious questions about money going to support the Conservative party and those working on policy for any future Tory government." McShane has already said he is considering referring to the commission shadow chancellor George Osborne's alleged discussions about a donation to the Conservatives from Oleg Deripaska on his yacht in Corfu, which caused a political row this week.

Backstory

Pauline Neville-Jones was a career diplomat and former head of the Joint Intelligence Committee. She left the diplomatic service and joined investment bank NatWest Markets which advised the then Serbian president, Slobodan Milosevic, on a controversial telecoms privatisation. She then had a stormy period as a BBC governor.