Slovenia sent a protest note to Croatia last Friday accusing it of claiming the part of the Adriatic Sea, which the successors to the former Yugoslavia have still not divided, by extending oil company INA's concession to drill for oil and gas in the Adriatic.
In a press release on Monday, Croatia's Ministry of Foreign Affairs and European Integration said it had sent Ljubljana a note vehemently protesting against Slovenia's attempt "to state, more directly than before, an open and clear intention to claim Croatian state territory, namely territory over which the Republic of Croatia has sovereign rights and jurisdiction".
The ministry said it would notify relevant EU and UN bodies as well as other international factors of Slovenia's attempt to claim foreign territory.
The ministry said it "rejects the interpretation that there is a so-called undivided Adriatic Sea, which is unacceptable under international law".
The sea is not and cannot be the subject of succession because it belongs to the land and depends on the land which Croatia succeeded as one of the successors to the ex-Yugoslavia, the ministry said.
Croatia adopted the decision to extend INA's concession under Croatian laws and the decision refers exclusively to Croatian state territory and territory on which Croatia has sovereign rights and jurisdiction, the ministry added.
The statement went on to say that the decision did not prejudge the sea border between Croatia and Slovenia, and that it did not clash with the 10 June 2005 joint statement on the avoidance of incidents.
Slovenia's actions, such as Friday's note, bring into question Slovenia's credibility due to arbitrary and open neglect as well as violation of the basic tenets of international law and international relations, said the statement.
The ministry described as unacceptable Slovenia's policy of refusing to settle the border issue before an international judicial body, whose decisions are binding and to which parties to a dispute refer voluntarily, choosing instead to strain relations with neighbouring Croatia.
Such a choice "is not and cannot be in the interest of either Slovenia or the Slovene public, who are entitled to a correct, objective and well-founded truth about the legal state of border issues with neighbours, including a legally founded and non-politicised approach to the issue of sea border demarcation with the Republic of Croatia," said the statement.
It also said that such a policy was "unacceptable and harmful also from the position of security and stability in Southeast Europe, where consistent respect for international law regarding borders represents the most sensitive and most important principle of lasting peace".