Swedish Prime Minister Fredrik Reinfeldt's conservative Moderates are losing ground in the run-up to the European parliament elections on June 7, an opinion poll showed on Saturday.

The Moderates, traditionally the second biggest party in Sweden, garnered 22.6 percent of voter sympathies in the Sifo poll conducted May 18-28 among 1,896 people and published in Svenska Dagbladet newspaper.

That was a drop of 1.3 percentage points from Sifo's previous poll conducted a month earlier.

The biggest party, the Social Democrats, also saw a slight dip in support, of 0.2 points, to 31.7 percent.

Meanwhile, one of the biggest sensations in the Swedish EU parliament election campaign is the pro-piracy Pirate Party.

It was expected to win 6.0 percent of votes, according to Sifo, gaining 0.1 point from a month earlier. That would be enough to earn at least one seat in the parliament.

Founded in 2006, the Pirate Party "wants to fundamentally reform copyright law, get rid of the patent system and ensure that citizens' rights to privacy are respected," it says on its website.

It took 0.6 percent of the vote in Sweden's 2006 general election, but has seen a surge in support after a Stockholm court in April found four men guilty of promoting copyright infringement for running one of the world's biggest filesharing sites, The Pirate Bay, and sentenced them to a year in prison.