Taoiseach Enda Kenny has claimed that Ireland's credit rating would be downgraded if the fiscal treaty is rejected in Thursday's referendum.
Mr Kenny said Finance Minister Michael Noonan was correct when saying a No vote would lead to tougher budgets.
He said a number of rating agencies had indicated that if the people turn down the treaty, a downgrading of the country would follow.
Meanwhile, voters on five islands off the coast of Donegal cast their ballots on the fiscal treaty referendum today.
Up to 750 people were eligible to vote there.
The ballots will be taken to the mainland and then to the count centre in Donegal Town on Friday morning.
People Before Profit TD Richard Boyd Barrett claimed a "time bomb of austerity" will go off if the fiscal treaty is passed.
Speaking at the final PBP news conference of the referendum campaign, Deputy Boyd Barrett said there would be billions of euro in further cuts and tax increases when Ireland exits the bailout programme.
Minister for Transport, Tourism & Sport Leo Varadkar has warned that a No vote in the fiscal treaty referendum would probably mean a "more difficult budget" in December.
Speaking on Morning Ireland, Minister Varadkar said if Ireland votes No on Thursday, the Government would have to operate on the assumption that there would be no funding for the country at the end of next year.
He said the Government would then be forced to "hawk around the place" looking for money for the country.
People Before Profit TD Joan Collins said there is a mood across Europe against austerity and this will be reflected in voting on Thursday.
She said: "I think a No vote from the Irish citizens will link ourselves into that mood against austerity, force the European Commission and the ECB to sort of realise you cannot break the social contract that has been part of European policy since World War II."
Minister for Finance Michael Noonan has said it is important that people know the full implications of a No vote before they place their votes on Thursday.
He said the uncertainty created by a No vote would result in growth estimates for next year being marked down and also result in those planning inward investment in Ireland stalling on their decisions.
He said a No vote would mean no access to the ESM funds at the end of the current bailout period, and that would mean he would have to speed up the correction, and plan a tougher budget.
Mr Noonan said he hoped the Yes vote would prevail and this would not be necessary.
Blair Horan urges Yes vote
A group of trade unions urging a Yes have claimed that a No vote would trigger savage cuts in pay and welfare benefits.
Secretary of the Charter Trade Union Group Blair Horan warned that it could also lead to a default on debt and exit from the euro, which could cost Ireland €11,500 per person in the first year alone.
He said it was clear that the ESM bailout fund would be the only option for Ireland in 2014 if markets were closed.
He claimed that without access to the fund, pay for public servants, pensioners and those on social welfare benefits would face cuts, which he described as "savage".
Mr Horan - who recently retired as general secretary of the Civil Public and Services Union - cited a paper from UBS Group last September which estimated the cost of leaving the euro for Ireland at €11,500 per person in the first year, and €4,000 per person in subsequent years.