Support for the EU Lisbon treaty is strengthening in recession-hit Ireland, according to a poll showing 52 per cent would vote "yes" if a second referendum were held on the issue.

The Irish Times/TNS mrbi poll found support has increased by one point on a similar survey in February, while the percentage of "no" voters has fallen four points to 29 per cent. Nineteen per cent said they did not know, up three points.

The newspaper said support for the Lisbon treaty "has consolidated over the past three months", largely as a result of the severe economic downturn here.

In a shock result in a referendum last June, 53.4 per cent voted "no" and 46.6 per cent voted "yes", sparking a major crisis in the EU.

Of the 27 EU nations, only Ireland is constitutionally bound to hold a referendum on the treaty, which is designed to improve decision-making in a greatly expanded bloc. It must be ratified by all member states.

Ireland is seeking a number of guarantees from Brussels, including on the right to make its own laws on tax, defence and abortion, before holding another vote, likely before the end of October.

When the pollster excluded undecided voters, 64.5 per cent of respondents in yesterday's poll backed the Lisbon treaty and 35.5 per cent opposed it.

When asked if, in the light of the economic crisis, it was better to be part of the EU, 79 per cent agreed it was, down one point since February. Ten per cent thought it was not (down three) and 11 per cent had no opinion (up four points).