The Premier League failed to enforce an official ban on Owen Oyston being the owner and a director of Blackpool following the club’s promotion in 2010, the Guardian has learned.

The Premier League took the view that Oyston’s 1996 conviction for rape, which can never be legally “spent”, meant that he was not a “fit and proper person” and that he was disqualified from being an owner or director of a club. Richard Scudamore, the league’s chief executive, insisted that Oyston dispose of his majority shareholding in Blackpool – and thought he had done so – but Oyston never complied with the disqualification. He remained the club’s owner and a director during the 2010-11 Premier League season and throughout Blackpool’s subsequent years in the Football League.

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During this time he and his son Karl transferred £26.77m out of Blackpool to Oyston companies. Following a legal action brought against them by Valeri Belokon, a Latvian banker who had invested alongside them, those payments were found by a high court judge in November to have been an “illegitimate stripping” of the club.

The £26.77m included £11m Blackpool paid Owen Oyston’s company, classed as a director’s salary, for his services during the 2010-11 season – despite his having being told by Scudamore that he was officially disqualified as an owner and director. Owen Oyston has also taken legal action against some supporters for comments made in protest on social media, which caused them serious financial worries. Thousands of Blackpool fans have boycotted matches, refusing to pay money to the club until the Oystons leave.

The Premier League differed in its view of Oyston’s rape conviction from the EFL, which has allowed him to remain the club’s owner and a director. The “fit and proper person test” was introduced in 2004, banning people from being owners or directors if they have unspent criminal convictions involving dishonesty, or have twice been directors of clubs which have fallen insolvent. To secure clubs’ assent to the rules, the EFL established that any conduct before 2004 would not be taken into account.

However, after Blackpool were promoted in 2010, the Premier League did not adopt that stance. In December 2010, after discussions, Scudamore agreed that the rule would be complied with if Owen Oyston transferred his shares to Karl. Scudamore assumed that had been agreed but in March 2011 Owen Oyston wrote to the Premier League, protesting principally about incurring a large tax bill if he had to dispose of his shares.

He proposed instead agreeing not to be involved in any substantial management of Blackpool without consulting the league. Scudamore, however, said the board did not consider that acceptable and insisted that Oyston transfer his shares. That never happened and within weeks Blackpool were relegated. The Premier League is understood to have told Owen Oyston it would require him not to be the owner if Blackpool were promoted again.

Last month Karl left the club and other Oyston companies following a serious falling-out with his father over the handling of the Belokon legal action. Belokon has the legal power to enforce a sale of Blackpool and any other Oyston assets but he is barred from being an owner or director because of a criminal conviction in Kyrgyzstan, in his absence, for money-laundering.

Belokon said in a statement that he contested the validity of the conviction, claiming it was politically motivated and “ignored the most basic principles of natural justice”. He said he was working to persuade the EFL that “there are obvious and compelling reasons why I should be considered to be a fit and proper person under the EFL rules”.

Andy Higgins, vice-chair of the Blackpool Supporters’ Trust, which is campaigning for football to have an independent regulator, said he was disappointed to find that the Premier League had not enforced its disqualification of Owen Oyston. “If the Premier League had implemented its ban, millions might not have been taken out of the club and it could have saved us all this heartache,” he said.

The Premier League declined to comment.