The UK-based Russian billionaire oligarchs Mikhail Fridman and Petr Aven have had their shares in the $22bn (£17bn) conglomerate LetterOne, which owns Holland & Barrett, “frozen”, days after they were hit with EU sanctions following Russia’s invasion of Ukraine.

LetterOne, which is just under 50% owned by Fridman and Aven, announced on Wednesday night that the men had “ceased to have any involvement with the company” and that it had frozen their shares.

Lord Davies, the company’s chair and a former Labour trade minister, told the Guardian: “Mikhail Fridman and Petr Aven have ceased to have any involvement with the company. Their shares are frozen and they will not receive dividends, expenses, information or access to the business.”

As a result, Davies said, the company was “not controlled by sanctioned individuals”. The billionaires, who have said they will “contest the spurious and unfounded basis” for the imposition of EU sanctions, will not be able to sell their stakes in LetterOne while they remain blacklisted. They will also be barred from entering LetterOne’s offices or speaking to any employees.

Fridman and Aven were placed on the EU sanctions list on Monday. They are not under UK or US sanctions. Fridman was described by the EU as “a top Russian financier and enabler of Putin’s inner circle”.

Aven was described by the EU as “one of Vladimir Putin’s closest oligarchs”, and an “especially close personal friend” of the Rosneft chief executive, Igor Sechin. “He is one of approximately 50 wealthy Russian businessmen who regularly meet with Vladimir Putin in the Kremlin,” the EU document added.

The men have denied any “financial or political relationship with President Putin or the Kremlin” and said they would “contest the spurious and unfounded basis for the imposition of these sanctions – vigorously and through all means available to them.”

Fridman, who was listed as the UK’s 11th wealthiest person in the Sunday Times Rich List with an estimated £11bn fortune, owns Athlone House, a £65m mansion in Highgate, north London.

Aven, who has an estimated $5.5bn fortune, owns Ingliston House, near Virginia Water, on 8.5 acres of land in a gated estate next to Wentworth golf course. It boasts an art collection including works by Larionov, Goncharova and Kandinsky, as well sculptures by Louise Bourgeois, Henry Moore and Antony Gormley in the garden.

The men said the EU sanctions were “malicious and deliberate falsehood”. “Pure and simple, the product of historical fantasies and conspiracy theories dreamed up by private individuals with their own agendas,” their representatives said on Tuesday. “They will fight this injustice with every sinew – for themselves and the tens of thousands of employees in the UK and Europe who rely on them.”

LetterOne, which was created by Fridman and partners with proceeds from the sale of TNK-BP after it was bought out by Kremlin energy giant Rosneft, owns a swathe of energy assets across Europe as well as Holland & Barrett and the Spanish supermarket group Dia.

Davies said he would work to support the more than 120,000 people who work for LetterOne and his “focus is to strengthen the board to ensure these jobs are protected”.