SINN Fein is poised to make massive gains in the Republic, with the latest opinion poll predicting that the party will have an MEP elected in each of the south's three European constituencies.

The Millward-Brown survey carried out for The Sunday Independent puts the party in first position going into Friday's European poll in the south. Sinn Fein has seen its support increase by three percentage points to 23 per cent, putting it one point ahead of Fine Gael.

The same poll has support for Fianna Fail dropping by two percentage points to 11 per cent and Labour slipping by a similar margin to 10 per cent.

Commentators are attributing the backlash against the Republic's ruling Fine Gael-Labour coalition to imposition of water charges.

The survey shows how three out of four people believe the charges will not be "fair and equitable" as promised by Enda Kenny. Just 16 per cent of those polled agreed with the taoiseach's assessment.

The opinion poll also indicates that Gerry Adams's arrest in connection with the 1972 abduction and murder of mother-of-10 Jean McConville has not damaged his party's electoral prospects.

In Dublin, the survey predicts Sinn Fein's candidate Lynn Boylan will top the poll, with her support surging by three points to 23 per cent.

However, Fine Gael's Brian Hayes is expected to mount a strong challenge in the capital and has seen his support increase by seven points in recent weeks to 22 per cent.

Independent MEP Nessa Childers, who won a seat for Labour in 2009's European election but quit the party after falling out with the leadership, is marginally ahead in the battle for Dublin's third seat, despite her support falling by six points to 13 per cent.

Meanwhile, north of the border one commentator has tipped Sinn Fein to again top the European poll - giving it an MEP in all four Irish constituencies.

Politics professor Richard Wilford from Queen's University Belfast said: "There is no doubt that Sinn Fein will hold the seat in the north and probably top the poll.

"The results won't demonstrate any growth because the Sinn Fein vote has plateaued."

Mr Adams (65) was released from Antrim police station two weeks ago after four days of questioning by detectives about the murder of Mrs McConville and other alleged links with the IRA.

His arrest prompted deputy first minister Mr McGuinness to claim that a "dark side" at the PSNI was behind his detention, an allegation Chief Constable Matt Baggott and senior commanders have denied.

"I don't think you should construe the improved performance in any way being directly correlated with the arrest of Gerry Adams," Professor Wilford said.

"The electorate north and south are very different and for the southern electorate it is a plague on all the houses of the other major parties because of austerity."

The Queen's academic said the unionist vote could be splintered but not shredded by the number of candidates running.

The DUP considered fielding two but decided against it, meaning the party's Diane Dodds and the Ulster Unionists' Jim Nicholson are favourites to be returned to Brussels.

Last time, Traditional Unionist Voice leader Jim Allister, who opposes power-sharing with Sinn Fein while sitting in the Northern Ireland Assembly, did well but professor Wilford doubted he had the same momentum this time.

"If he exceeds it this is going to be a message that the DUP simply cannot ignore," he said.

"It will sour what is already a fairly toxic atmosphere."

* SUPPORT: QUB politics professor Richard Wilford expects Sinn Fein to top the European poll in the north, but does not believe that the arrest of Gerry Adams earlier this month will have much bearing on the outcome PICTURE: Brian Lawless/PA