Sinn Fein remains on course to emerge from the Stormont election as Northern Ireland’s biggest party, a new opinion poll indicates.

The party’s popularity has risen to 27%, extending its lead over the DUP to almost seven points, according to the survey of voter intentions.

The findings of the Institute of Irish Studies-University of Liverpool/Irish News poll are broadly in line with other surveys over recent weeks and months, all of which have put Sinn Fein in front and with a significant gap between it and the second-placed DUP.

The last University of Liverpool poll of decided voters in February had Sinn Fein on 23.2% of first preference votes and the DUP on 19.4%.

5 Leaders, 5 Days event
DUP leader Sir Jeffrey Donaldson faces a battle to retain the party’s pre-eminent position at Stormont (Liam McBurney/PA)

While the DUP has made a slight gain seven weeks on, rising to 20.2%, Sinn Fein has surged ahead with a 3.8 point increase on its February standing.

If polling data is borne out at the May 5 Assembly election, Sinn Fein would displace the DUP as the region’s largest party – a position it has occupied for almost 20 years – and it would be entitled to take the role of first minister, with Michelle O’Neill the party’s likely choice for the job.

However, there is uncertainty whether a functioning executive will be formed post-election.

The Executive collapsed in February when DUP first minister Paul Givan quit in protest over Brexit’s Northern Ireland Protocol and the barriers it has created on the movement of goods between Great Britain and the region.

The DUP has made clear it will not be returning to an executive before major changes are secured to the contentious Irish Sea trading arrangements.

The opinion poll also indicates that unionist concern about the protocol is rising.

In February, 11.7% of unionists ranked it as their biggest concern. That figure is now up to 20.9%, though it remains lower down the priority list for unionist voters than the economy (29.8%) and health (25.5%).

Of nationalist voters surveyed in the latest poll, only 2.1% ranked the protocol as their main concern – well behind health (31%) and the economy (30.2%).

Powersharing rules mean a properly functioning administration can only be formed if the largest unionist and largest nationalist parties agree to enter the joint office of the first and deputy first ministers.

Aside from the protocol, both the DUP and UUP have repeatedly refused to confirm whether they would take the post of deputy first minister alongside a Sinn Fein first minister.

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Unionist concern over the Northern Ireland Protocol is rising, according to the opinion poll (Peter Morrison/PA)

The roles of first and deputy first minister are equal in law and one has no more power or authority than the other. While Sinn Fein has held the deputy first minister role for much of the last 15 years, it has yet to be in a position to take the first minister’s job.

Of the other parties, the cross-community Alliance Party looks set to build on recent strong electoral showings.

Despite a one-point drop from February, the poll still places it as the third most popular party at 14.6%.

The Assembly election uses the single transferable vote system of proportional representation, which gives voters the opportunity to rank other parties in order of preference after selecting their first choice.

The opinion poll places Alliance out in front when it comes to the most popular party for transfer votes – something that could prove crucial in close-run battles in the region’s 18 five-seat constituencies.

According to the survey, the UUP comes in fourth in the popular vote, on 13.5% – down a half point from February.

The SDLP, in fifth, is up slightly on its standing seven weeks ago, rising from 9.9% to 10.3%.

Of the smaller parties, support for the Traditional Unionist Voice (TUV) party has slipped back one point to 5.4%.

The Green Party NI has also fallen back, dropping two points in seven weeks to come in at 4.3%.

Support for People Before Profit has fallen as well, down slightly from the 2.3% it recorded in the last survey to 2.1%.

The opinion poll also found that 17.2% of voters have still to decide who they will give their first preference to.

Institute of Irish Studies director Professor Peter Shirlow told the Irish News that while support for the DUP had lifted “slightly”, it still looked like Sinn Fein was on course to displace it as the largest party.

“The DUP may be aided by the decline in support for the TUV and the significant share of unionists yet to decide,” he said.

“The SDLP and UUP are pretty much where they were in 2017, while Alliance seems to be holding the 2017-19 electoral surge – these three parties need to transfer between each other to ensure seats are gained or at least not lost.”

The poll of 1,000 voters was conducted between March 11 and 26 by Social Market Research Belfast and has a margin of error of 3.1+/-.