Ireland had ceded too much control to "unaccountable" European institutions, the Sinn Féin president, Mr Gerry Adams MP, said at the launch of his party's campaign for a No vote in the second Nice referendum.
A party spokesman said Sinn Féin would be spending €60-€70,000 in its campaign, compared to about €12,700 in the first referendum.
The party says it has increased its membership since the general election - by almost 25 per cent in Dublin for example - allowing it to conduct a more intense door-to-door canvass against Nice.
At a news conference in a Dublin hotel, Mr Adams accused the Government of having an "à la carte attitude to democracy". He said there had been "scaremongering, bullying and negative campaigning" but very little positive debate.
"More and more people are beginning to ask if the gradual erosion of our sovereignty and our neutrality has gone too far. Many more people are beginning to see that we have ceded too much control to unaccountable institutions."
He continued: "People just don't understand and have not been told why there is a replay. We can't take it for granted, but I think the people will vote No again. But just say people voted Yes: does than mean we are going to have a draw?"
Mr Caoimhghín Ó Caoláin TD said: "A referendum can have no democratic value in this State if a government can defy its outcome and then return to the people seeking a reversal of their decision."
The chief campaign organiser, Mr Daithí Doolan said the party would be mounting an "intensive ground campaign" for a No vote.
"Our membership played a vital role in the defeat of the Treaty last year and they are eager to do so again. We are currently distributing over half a million newssheets on Nice along with tens of thousands of canvass cards and leaflets.
"We will be putting up approximately 7,000 posters and we are holding public meetings across the country."
He continued: "We are aware that we cannot outspend the Yes campaign but what will win this referendum is engaging with the people and informing them. This is what defeated the treaty last time and this is what will do so again."
He said the campaign would be financed from central party funds and the local Sinn Féin organisations. "Each constituency has to pay for its own literature."
Meanwhile, the former regional secretary of the ATGWU, Mr Mick O'Reilly, challenged the Government to "come clean" about its intentions if Nice was defeated a second time.
At a meeting of shop stewards in Waterford, he said, "Will the Government just keep holding referenda until they get the result they want?" He denied Nice would have adverse economic effects.
"We didn't need the Nice Treaty to create the boom in the 1990s, nor will our rejection have any effect on foreign investment - just look at the UK economy."
The Independent MEP for Connacht-Ulster, Mrs Dana Rosemary Scallon, said in a statement issued at the European Parliament in Strasbourg: "A No to Nice vote will not result in repercussions or sanctions on Ireland from our European partners. Ireland will still be a full, participating and committed member of the EU."
She added: "Ireland's No to Nice highlighted the flaws in the Treaty and the democratic deficit within European institutions. The democratic decision of the Irish people in rejecting Nice is being ignored by our own political leaders and by Europe; indeed we are in danger of losing both our sovereignty and independence."