DUBLIN (Reuters) - Irish nationalists Sinn Fein have surged to the top of an opinion poll five days ahead of an election in Ireland that looks set to be a major breakthrough for the former political wing of the Irish Republican Army.

FILE PHOTO: Sinn Fein Leader Mary Lou McDonald in Brussels, Belgium April 1, 2019. REUTERS/Francois Lenoir

An Irish Times/ Ipsos MRBI poll published on Monday found support for left-wing Sinn Fein at 25%, making them a clear leader, with support for centre-right Fianna Fail at 23%. Support for governing Fine Gael was 20%.

Fine Gael and main opposition Fianna Fail both refuse to govern with Sinn Fein, citing their IRA links and opposing economic policies.

Sinn Fein, whose members were banned from speaking on Irish media until the mid-1990s before the end of Northern Ireland’s three decades of conflict, is part of a power-sharing government in the British-run province, which it ultimately wants to reunite with the Irish Republic.

The party has said it will not go into coalition government without a commitment to immediately start planning for a referendum on the unification of Ireland, a vote it would push to be held within five years.

Approval for the government, Prime Minister Leo Varadkar and Fianna Fail leader Micheal Martin all fell as Sinn Fein leader Mary Lou McDonald shot up seven points to 41% to become the post popular among all the main parties.

Despite the poll, Sinn Fein are unlikely to emerge as the largest party as it is running only 42 candidates, which is around half the number of candidates being fielded by both Fine Gael and Fianna Fail.

Sinn Fein would need to get almost all 42 elected to the 160-seat chamber to give it a shot at emerging as the largest party.

Getting such a return would be difficult for any party, analysts say. Ireland’s proportional representation system also favours parties running more than one candidate in larger constituencies.

A senior member of the Sinn Fein front bench David Cullinane responded to the opinion poll on Twitter by criticising journalists who questioned his party’s strategy.

“We are standing enough candidates to be serious contenders for Government. The demand for change is heart lifting.”

Earlier on Monday, Ireland’s national broadcaster RTE reversed a decision to exclude party leader McDonald from a televised debate scheduled for Tuesday evening.

The broadcaster had planned to restrict the debate to Varadkar and Martin, the leaders of the two parties it considered most likely to lead the next Irish government based on empirical data.