THEY come with the strongest possible 'health warning', the type that flashes in brightest neon. Local opinion polls emerged as a feature of the 2002 general election. And with results from almost 20 surveys already published, they are back again, with the local newspapers owned by the Crosbie Group set to publish another seven local polls over the next few weeks. The 'health warning' arises from the fact that these polls are defined by small sample sizes and large margins of error, and while some are carried out by reputable market research companies, others are nothing more than vox pops by provincial newspapers.

The experience from 2002 showed that it is dangerous to use local polls to predict the actual result in Dail constituencies. The situation in Kerry North in the run-up to the 2002 election testifies to this. A poll commissioned by TG4 in October 2001 predicted that Martin Ferris of Sinn Fein would win a seat in Kerry North at the expense of Fianna Fail. Four months later, a poll commissioned by RTE's Prime Time suggested that Ferris would miss out and the party status quo would prevail, with a seat each for Fianna Fail, Labour and Fine Gael. But when polling day came, the Sinn Fein politician did in fact take a seat. The loser was former Labour leader Dick Spring, whose position was predicted to be secure according to all the pre-election local polls.

In another case, Jim Higgins of Fine Gael saw his first-preference vote range widely in his Mayo constituency from 9% to 18% in three different local opinion polls published within six days of each other in April 2002. (In the end, Higgins narrowly lost out on election day. ) Michael D'Arcy was another Fine Gael loser in 2002. The long-time Wexford TD blamed his loss on what he described as a "Mickey Mouse" poll in a local newspaper. The Wexford poll gave the Fine Gael politician 3% of the first-preference vote. D'Arcy's experience led him to call for a ban on the publication of results from uncredited opinion polls.

His unhappiness found support in an academic review of the 2002 experience of opinion polls. In an assessment of local poll performance at the last general election, Gail McElroy and Michael March, two Trinity College political scientists, concluded that "regional journalism and survey research make for strange bedfellows".

National opinion polling has been a feature of Irish elections since 1977.

The leading companies have a decent record in predicting election outcomes but problems emerged in 1997 and 2002. Indeed, all the national opinion polls in 2002 overestimated the Fianna Fail vote and underestimated the vote for Fine Gael.

A variety of explanations have been put forward for this, including the impact of a late swing in voter preference between the final opinion poll and the actual election. In the controversy generated by the inaccuracy of national polls in 2002, the accuracy . . . or otherwise . . . of local opinion polls was somewhat overlooked.

The last general election was the first to feature a significant number of local constituency polls. In their review of the local polls in 2002, McElroy and Marsh focused on 31 local surveys of voter intentions. Compared to the national opinion polls, which significantly overestimated Fianna Fail support, McElroy and Marsh found that "the local polls do a slightly better job of predicting the overall Fianna Fail vote". They also found that while Fine Gael support was underestimated in the national poll, its vote was "substantially over-estimated in the local polls" by as much as 2.4%.

Taking that health warning into account, several trends have emerged from recent local polls. These surveys of local opinion undertaken by well-known market research companies show a remarkably solid out-turn in the Fianna Fail vote.

Fianna Fail's vote has fluctuated between 36% and 41% in a variety of national polls undertaken since last autumn. But, in the more recent local polls, Fianna Fail's incumbent TDs have been polling strongly. Even where the party's first-preference vote is down on 2002 levels, many seats may just be saved with well-known names on the ballot paper and tight vote management in the constituencies.

Some constituencies such as Galway West and Mayo have been polled more than once with different results.

In Galway West, polls suggest the two Fianna Fail incumbents, Eamon O Cuiv and Frank Fahey, are more than comfortable, with Michael D Higgins of Labour set for another Dail term.

The final two seats will be fought over by a collection of candidates including Padraic McCormack of Fine Gael and Noel Grealish of the Progressive Democrats (both outgoing TDs), as well as Mike Crowe of Fianna Fail and Niall O Brolchain of the Green Party.

The differences between those four candidates have been so small in both Galway West polls that each of these politicians can still hope for victory on election day.

There was a similar outcome in Mayo which has been polled three times in recent months. These local polls, undertaken by different market research companies, show Enda Kenny and Michael Ring battling to top the poll. Fine Gael is sure of two seats and Fianna Fail newcomer Dara Callery looks set to take a seat, but after that the constituency is a very close contest.

The collection of local poll results shows the final seats in Mayo will be shared by two people from groups including a second Fianna Fail candidate, a third Fine Gael candidate or one of the two sitting independents, Jerry Cowley and Beverly Flynn.

These differing outcomes are hardly surprising as polls are merely snapshots of the voter mood at a given time. Those polls conducted well in advance of the actual general election are more likely to see the electorate influenced by non-election matters.

The most recently published local opinion poll came last week in Kildare South. It again showed Fianna Fail's vote holding up, with its two seats more than secure, while Labour's Jack Wall is set to poll strongly. The status quo will prevail in Kildare South, according to the poll in this three-seat constituency, with Fine Gael's vote as depressed as it was in 2002.

Interestingly, however, the poll showed the Green Party first-preference vote in Kildare South increase from the 3% at the 2002 general election. But this time JJ Power, a brother of Fianna Fail junior minister Sean Power, looks set to benefit from an upswing in support for his party. The local poll put the Green candidate at 10% in Kildare South, not enough to win a seat but a significant improvement on 2002.

Across the other local opinion polls the Green trend has also been in evidence. Recent local polls have predicted that Mary White will take a seat in Carlow-Kilkenny, Patricia McKenna will win in Dublin Central and Niall O Brolchain will be elected in Galway West. If these opinion-poll results come true on election day, then the only colour the neon will be flashing in 2007 will be green.