Russia's President Vladimir Putin has for years developed links to extremist parties in Europe.
The latest polling shows that populist Nigel Farage's Brexit Party is likely to gain the most votes in the UK, and establishment parties — battling to win back alienated voters — are forecast to lose their EU majority.
Austrian Chancellor Sebastian Kurz called time on his coalition government with the far-right Freedom Party. Kurz said he was seeking the removal of the country's interior minister, Freedom Party politician Herbert Kickl, to ensure an unbiased probe into the video. The Freedom Party reacted by withdrawing its ministers from the government.
Kickl's removal follows the resignation of Freedom Party leader Heinz-Christian Strache, who was also Austria's vice-chancellor.
That came a day after two German newspapers published a video showing Strache pandering to a woman claiming to be a Russian tycoon's niece at a boozy gathering in Ibiza two years ago, shortly before national elections.
Overall, establishment parties across the continent are expected to suffer this week, both at the hands of the populist-right as well as resurgent liberal parties. The result is likely to be a more fragmented European Parliament.
In Britain, the latest polling average puts the Brexit Party ahead of the two major parties, on 32 per cent compared to Labour's 21 per cent and the Tories' 11 per cent. This would mark the Conservatives falling to their lowest vote share in a national election since 1834. The Lib Dems are ahead of the Conservatives in second place on 15 per cent.
At a continent level, the EU's established centre-left and centre-right blocs are likely to lose their combined majority in the elections. The latest Politico analysis indicates that the two large pan-European blocs, which are comprised of allied parties from each EU country, will lose seats under a tide of both populist and liberal support.
While the centre-right European Peoples' Party (EPP) and centre-left Socialists & Democrats (S&D) are likely to remain the largest parliamentary groups, experts warn that their dominance is now "threatened". Forecasts indicate they will lose 98 seats between them, compared to their 2014 election result.
The loss of their combined majority is thanks to the rise of the liberal Alliance of Liberals and Democrats for Europe (ALDE) and eurosceptic Europe of Nations and Freedom (ENF). These parties are forecast to pick up an extra 38 and 36 seats, respectively.
- Telegraph Group Ltd, AP