Mario Giro also said that the EU could not accept the UK becoming a tax haven on its doorstep.
He told BBC Newsnight: "Everything is negotiable and then also deliverable, everything.
"On one side the White Paper is a wish list, with no precision on how to handle it. It's main things are 'what we want', what UK wants in this negotiation.
Italy's deputy foreign minister Mario Giro criticised Brexit's White Paper
"But, on the other side, the tonality of the white paper is a good one … The white paper says more or less what are the best results for both."
After Prime Minister Theresa May threatened that Britain could cut its tax rates to attract investment if it did not get the deal it wanted from the EU, Mr Giro said Brussels would resist such a move.
"We cannot accept that UK will become a tax haven near to Europe."
Mr Giro said Britain cannot become a 'tax haven'
I think it is a daunting task for both because, of course, it's a divorce. In a divorce, divorce is always painful and it's a failure
Mario Giro, Deputy foreign minister
Mr Giro said Britain's divorce from the EU would be painful for both sides.
"I think it is a daunting task for both because, of course, it's a divorce. In a divorce, divorce is always painful and it's a failure. We are all responsible, and we have to act quickly, and with fairness.
"I mean quickly also because I know that it is very complicated and we don't know exactly how to handle it. It is the first time. I say that we need to be quick because the financial markets let us no time."
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BORDER-FREE Schengen: Countries you can visit WITHOUT a passport
Mon, January 23, 2017
If you are an EU national, you do not need to show your national ID card or passport when you are travelling from one border-free Schengen EU country to another. The Schengen Area is an area comprising 26 European states that have officially abolished passport and any other type of border control at their mutual borders.
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Asked what would be the most difficult aspects of the negotiations, he said: "Probably the commercial thing … because, of course, the common market is very important for us, it's the building block of the EU, and we need to speak a lot about that."
The document indicated Britain looks likely to quit the European Customs Union.
The Italian politician admitted the EU does not know how to handle the 'divorce'
It also said the UK could become subject to a new arbitration panel to resolve disputes with the EU after it removes itself from the jurisdiction of the European Court of Justice.
It made clear that Brexit would not happen as an abrupt "cliff-edge" moment, because changes including new immigration controls, customs systems and business regulations would be phased in gradually.
Mr Giro's comments came as Mrs May was meeting fellow EU leaders at a summit in Malta.