A top EU official on Thursday accused several European countries, including Ireland and the Netherlands, of being tax policy "black holes" and promised to pressure them to change their ways.

"Obviously many countries in the European Union are places where aggressive tax optimisation finds its place," EU Economic Affairs Commissioner Pierre Moscovici told reporters in Brussels.

"Some European countries are black holes (...) I want to address this," he added.

Former French finance minister Moscovici spoke ahead of an EU finance ministers meeting in which the bloc was expected to whittle down a month-old blacklist of non-EU tax havens from 17 countries to nine.

When the list was announced in December, NGO Oxfam said four European countries -- Ireland, Luxembourg, Malta and the Netherlands -- deserved to be on the list if the EU's criteria were being faithfully applied.

Moscovici denied this, but added: "If you realise that the tax flows go to this or that country: Ireland, the Netherlands, Luxembourg, Malta, Cyprus (...), let's talk about how to solve things."

These countries often serve as EU headquarters for global multinationals, offering complicated tax schemes that help companies -- such as Google, Apple or Facebook -- to shift profits and avoid big tax bills.

But instead of expanding their list, the 28 EU finance ministers meeting on Tuesday are expected to absolve eight countries - including Panama and South Korea.

They will now go to a so-called "grey list", jurisdictions that have made unspecified commitments to the EU on reforming their tax laws.

Moscovici warned against breaking citizens trust and called on ministers to make public any commitments made, repeating similar pleas in European Parliament.

"We cannot accept that member states are secretly negotiating exemptions for tax haven nations that have fallen in favour," said French MEP Eva Joly of the Greens party, a major advocate of fair tax policy.

The grey list, which currently includes 47 countries, will be complemented by the eight struck from the blacklist, including the United Arab Emirates, Tunisia, Mongolia, Macao, Grenada and Barbados.