The Oyston family, owners of Blackpool, have been accused at the high court of treating the football club as “the family’s personal cash machine”.

Lawyers for the Latvian millionaire Valeri Belokon, the club’s president, were launching what could prove to be one of British football’s most expensive legal actions. Andrew Green QC alleged on Monday at the start of a five-week hearing that Owen and Karl Oyston, owner and chairman of the Lancashire club, had “improperly” extracted millions of pounds from its funds following promotion to the Premier League in 2010 and used the money for their own benefit.

Belokon’s company VB Football Assets, a minor shareholder in the club, was excluded from key decisions, information and any share of profits, Green said.

VB Football is pursuing a claim against the Oystons for “unfair prejudice” against shareholders. The claim is also against Blackpool FC Ltd itself and Blackpool FC (Properties) Ltd, a company with family links formerly known as Segesta. The Oystons are vigorously denying the claims in what has developed into a bitter legal battle.

Green told Justice Marcus Smith, sitting in London, that as a result of the Seasiders reaching the Premier League, the club received £106m. The unprecedentedinflux of cash over five years included £48m in respect of the 2010-11 season, followed by £58m in parachute payments after Blackpool’s relegation at the end of the season.

Green said: “Owen and Karl Oyston have treated Blackpool Football Club as the Oystons’ personal cash machine.” The QC said the family’s case was that at all times they had been transparent and open in relation to payments made out of the club. “Our case is this is simply inconsistent when you consider the documents. There was, in fact, the adoption of a deliberate strategy by the Oyston family to take cash out of Blackpool Football Club and do so in a way VB Football Assets and its nominated directors could do nothing to stop what was the antithesis of transparency.”

Belokon won a court case in Manchester in February this year in a dispute with the Oystons over his share of profits after he provided £4.7m in July 2008 to develop the south stand and south-west corner of the club’s stadium. That case was brought by JSC Baltic International Bank, owned by Belokon, against Segesta Ltd, the holding company for the club’s assets.

In March, the club announced Belokon was being suspended from its board as a result of a judgment in the Paris court of appeal related to disputed allegations of money laundering involving two banks founded or owned by him. The hearing continues.