Answering to numerous questions about her signature on the agreement, Ambassador Helena Drnovšek Zorko said on her Facebook account that she was instructed to do so by the government and that the signature did not express her personal opinion.

Drnovšek Zorko also published an opinion on a web portal, entitled "Why I signed ACTA", in which she says that she signed the document out of "civic negligence, because I wasn't attentive enough".

"I simply failed to connect the agreement which I had been authorised by the government to sign with the agreement which, in my opinion as a citizen, limits and takes away the freedom of work on the biggest and most important network in the history of humankind," the ambassador said.

Drnovšek Zorko explained that she had carried out her official duty while neglecting her duty as a citizen. "I don't know whether not signing was an option, but I could have tried," she said, offering an apology.

Rejecting speculations that she had signed the agreement secretly and on her own, she said that the accession to the agreement was the decision of the Slovenian government and the parliamentary EU Affairs Committee.

The Foreign Ministry said on Monday that the ministry and the Slovenian Embassy in Tokyo had no jurisdiction over the topics covered by the agreement and that they had not participated in its adoption.

On the government's proposal, the agreement was discussed by the Economy Ministry on 27 September and by the EU Affairs Committee on 7 October. The EU Council passed the decision on the signing of ACTA on 16 December.

The ambassador signed the agreement in line with instructions and authorisation from the government as the official representative of the country in Japan and not on her own, as follows from certain accusations on web portals, the ministry said.

The agreement was signed last week in Tokyo by representatives of the European Commission and 22 of the 27 EU member states, including Slovenia. The document is yet to be confirmed by the European Parliament and national parliaments.

Anonymous has meanwhile published on Youtube on Saturday a video accompanied by a text condemning ACTA, calling for protests and announcing attacks on the website of the Slovenian government.

"If the decision of the Slovenian parliament and representatives in the European Parliament is not a clear 'no', we will attack the website of the Slovenian government and publish documents and e-mails. We will show the Slovenian government that they cannot censor people."

The Public Administration Ministry, which manages the state administration's IT infrastructure, said it was taking the threat seriously and would respond to any attacks appropriately.

Protests against ACTA are scheduled to take place on Saturday in Ljubljana's Congress Square and Maribor's Leon Štukelj Square. Attendance has so far been confirmed on Facebook by more than 6,500 people.

"We are against ACTA, which threatens human rights and the freedom of the internet. The signing of ACTA has been a non-democratic process," says the Facebook invitation for the protests.

According to the website of the free daily Žurnal24, a Slovenian member of Anonymous has announced that the web attack will take place on the day of the street protest.