However, a spokesman for NOM in the US denied that it had channelled funds to any of the three main opposition groups. NOM was aware that foreign donations to lobby groups during referendums in Ireland were banned.
Some in the no campaign have countered with claims that the yes side has benefited from millions of dollars donated by the Irish-American multimillionaire Chuck Feeney and his Atlantic Philanthropies agency.
John Waters, the award-winning Irish columnist and writer, heads the First Families First group, which opposes gay marriage. Waters said it was outrageous that Feeney's agency had been "allowed to swamp the Irish democratic process".
Asked who funds his own group, Waters said: "We have no funding whatsoever and are not seeking any, being simply three private citizens seeking to defend certain constitutional rights and protections."
Atlantic Philanthropies declined to answer questions about the claims, but backers firmly rejected them.
Despite the accusations and counter-accusations over foreign money, the no camp appears to be facing an uphill struggle in its battle to defeat proposals to legalise gay marriage. A poll by Ipsos MRBI for the Irish Times last weekend found that 58 per cent will vote yes while 25 per cent will say no, with 17 per cent of the 1200 surveyed undecided.
- Observer