Slovenian member of the arbitration tribunal created to solve a border dispute with Croatia, Jernej Sekolec, resigned Thursday after a media scandal showed he had breached the tribunal's rules of impartiality.

"In the arbitration between the Republic of Croatia and the Republic of Slovenia, Dr. Jernej Sekolec has resigned from the Arbitral Tribunal," The Hague's Permanent Court of Arbitration said Thursday in a statement sent to AFP.

Croatian newspaper Vecernji List on Wednesday published a series of recordings of tapped phone conversations between Sekolec and the Slovenian government's intermediary dealing with the Tribunal, Simona Drenik, in which they openly discussed a common tactic that would lead to a ruling of the court favourable for Slovenia.

The arbitration court called the Slovenian authorities to propose a candidate to replace Sekolec in the arbitration tribunal tasked with solving the long-standing border dispute between Slovenia and Croatia.

"Once reconstituted, the Tribunal intends to resume its deliberations in the present arbitration without delay."

Meanwhile, Croatia threatened that it might withdraw from the proceedings.

"We are consulting our legal experts ... and we are reviewing all the possibilities including ... to withdraw from the arbitration" if it will be assessed that it was compromised, Croatian Foreign Minister Vesna Pusic told reporters in Zagreb.

Croatia has sent a letter to the European Commission over the issue, she said.

Although the arbitration is not under Brussels competency, Croatia has informed the Commission over the issue between two members of the 28-nation bloc, Pusic said.

"But, we will resolve our problem by ourselves," she stressed.

In 2009 the two former Yugoslav neighbouring countries Slovenia and Croatia signed an EU-backed deal agreeing to create an arbitration tribunal to solve their long-standing dispute over 13 square kilometres (five square miles) of largely uninhabited land and the Piran Bay in the northern Adriatic.

Each country was asked to propose a member of the five-member tribunal that would have to be impartial and, therefore, should not discuss the tribunal's work with the government.

Slovenian Prime Minister Miro Cerar confirmed Drenik had also resigned.

Slovenia, which has just 46 kilometres (29 miles) of coastline, believes its access to international waters is at stake because Croatia, whose Adriatic coast stretches for 1,700 kilometres, wants the border to be drawn down the middle of the disputed bay.

Earlier this month, the arbitration tribunal announced it would decide on the dispute by December. That decision will be binding for both countries.