MADRID (Reuters) - Spanish far-right party Vox said on Friday it would leave the European Conservatives and Reformists (ECR) group in the European Parliament to join a new alliance led by Hungarian Prime Minister Viktor Orban.

The move deals a blow to Italian Prime Minister Giorgia Meloni's hopes of securing the ECR's position as the third-largest grouping in the supranational legislative body and leading the opposition to the majority, which comprises moderate conservatives, social democrats and liberals.

"The patriotic forces that have seen their presence in the EP boosted have a historic opportunity to turn the voters' mandate into one great group that can become an alternative to the coalition between the centre-right, Socialists and the far left," Vox said in a statement.

It added that Orban's proposed group, dubbed Patriots for Europe, responded to the message of those who "demand a radical and urgent change of course" for the EU.

Vox leader Santiago Abascal said in an interview with La Gaceta newspaper that Meloni's Brothers of Italy party would "always be a partner, friend and ally of Vox" and thanked Poland's Law and Justice - which has so far refused to join Orban's platform - for being "at the vanguard of patriots' struggles in Europe".

Orban's Fidesz party has already wooed Austria's Freedom Party, the Czech Republic's populist ANO and Portugal's Chega to join forces through its new platform.

EP rules require groups to include parties from at least seven member states, so Patriots for Europe would still need to convince partners from two other countries to join in order to be formally constituted as a parliamentary group.

It is unclear whether the National Rally (RN), which won the first round of France's parliamentary snap election last week spearheaded by Marine Le Pen, will also join the group.

The Financial Times, citing three people familiar with the negotiations, reported on Friday that RN was in talks with Patriots for Europe and would announce a decision on Monday.

In the June 9 European election that saw far-right parties surge, Vox doubled its number of seats to six and garnered 1.69 million votes, nearly 300,000 more than in 2019.

(Reporting by David Latona; Editing by Gareth Jones)