Why this Irish election has changed the rules and what it means for the UK

  • Video report by ITV News Correspondent Geraint Vincent

Sinn Fein has emerged as the most popular party after Ireland's election on Saturday, securing the most first preference votes and topping the polls in the vast majority of constituencies.

They received 24.5% of the vote share on first preference, while rivals Fianna Fail and Fine Gael got 22.2% and 20.9%.

The almost-even split means it could be months before a new government takes power, as parties look to form coalitions between themselves to secure a majority in the Dail - the Irish parliament.

Sinn Fein President Mary Lou McDonald said she would form a "people's government" and pledged to tackle Ireland's housing and health crises.

Asked whether her party's performance was a "revolution" of Irish politics, she answered: "Yes, you could call it that for sure."

Sinn Fein MP Thomas Gould is elected in Cork North Central. Credit: PA

Who are Sinn Fein?

The left-wing Sinn Fein party campaigned to build more public housing, reduce childcare costs, lower the retirement age to 65, and bolster police numbers.

They're also an avowedly Republican party - and have pledged to introduce a referendum on whether Northern Ireland should leave the United Kingdom to join the Republic of Ireland.

They plan to establish a parliamentary committee and citizens' assembly to plan for Irish unity and Ms McDonald believes a referendum is likely "within the next five years".

"We now have a democratic pathway to Irish unity, to ending partition," she said.

The party has its roots in the Irish War of Independence in the 1920s, where they supported the original Irish Republican Army (IRA) against the UK.

The party split and took different sides in Ireland's civil war over whether to accept the peace treaty to the War of Independence, which partitioned Northern Ireland and left it out of the new Irish Free State.

After more splits and reformations, the party again came to prominence in Northern Ireland during the Troubles (1960s-1990s), where it campaigned for civil rights for the Catholic community and was linked to the provisional IRA as its 'political wing'.

Asked about the parties' past links to the paramilitary group, Ms McDonald said it didn't "achieve anything constructive".

"I think we have managed to construct a peace process over the last few decades which is robust and strong," she said.

  • Video report by ITV News Correspondent Geraint Vincent

Since the 1998 Good Friday Agreement, Sinn Fein have shared power with Unionists in Northern Ireland's Stormont Parliament.

They have long fielded candidates in the Republic of Ireland's elections - in 2007 they had four out of 153 seats.

But now, with first preference votes counted, they're in the lead.

(PA Graphics)

What are first preference votes?

The Irish system means voters select their 'first preference' on their ballot papers, followed by their second preference, third preference, and so on.

If their first preference does not receive enough votes to win that constituency, then their vote is transferred to their second preference, and so on.

The UK uses the first-past-the-post system, where voters only receive a single, non-transferable vote and the candidate with the most votes - but not necessarily the majority of votes - wins.

Votes were still being counted on Monday. Credit: PA

What will the next government look like?

Despite winning the most first preference votes, Sinn Fein only fielded candidates in 42 constituencies - half the number that Fine Gael and Fianna Fail each put out in the fight for 159 seats.

Fianna Fail, led by Michael Martin, remains best placed to secure the most seats, while Fine Gael looks to be the big loser and will concede several high profile-seats.

Fine Gael leader and current Taoiseach Leo Varadkar struggled to reclaim Dublin West, where he was outpolled by a Sinn Fein candidate, Paul Donnelly. Varadkar only got over the line after the fifth round of counting.

Current Irish PM Leo Varadkar barely reclaimed his seat in Dublin West. Credit: PA

Sinn Fein's unprecedented performance has broken the 90-year-long dominance of Fine Gael and Fianna Fail.

Both parties lean centre-right, and both have previously ruled out a coalition with Sinn Fein, opening up the possibility of a merger between the two historic rivals.

The last government under Mr Varadkar was already propped up by a historic confidence and supply deal with Fianna Fail.

It took 70 days to negotiate after an inconclusive result in the 2016 general election.

But Sinn Fein's overflow of votes could boost other left-leaning parties in Ireland, such as the Greens, Labour, the Social Democrats and Solidarity/People Before Profit - all of which will be courted by the three main parties as junior coalition partners.

Michael Martin's Fianna Fail looks set to get the most seats. Credit: PA

Fine Gael Finance Minister Paschal Donohoe said: "It is clear that no political party in our country has a monopoly on representing the people of Ireland."

But Ms McDonald said the proportion of votes Sinn Fein received earned it a place in government.

“This vote for Sinn Fein is for Sinn Fein to be in government, for Sinn Fein to make a difference, for Sinn Fein to be tested, for Sinn Fein to deliver," she said.

There are 160 seats in the Dail parliament.

The speaker is automatically re-elected, leaving 159 seats up for grabs and 80 the magic number for a majority.