Minister for Jobs, Innovation and Enterprise Richard Bruton has said the rejection of the fiscal treaty referendum would create uncertainty for investors.

Minister Bruton said companies considering investing in Ireland want certainty about Ireland's place in Europe.

He said Ireland has to be competitive and the country is already competing with Switzerland, Singapore and countries in eastern Europe.

Minister Bruton said these countries are offering attractive packages and investors do not want the instability of a political situation that is unclear.

He said: "We have to be competitive and we have to also give people certainty and the one that they do not want, if you're investing large sums of money, you do not want the instability and uncertainty of a political situation that is just totally unclear."

However, Sinn Féin's Peadar Toíbín rejected that argument and said a Yes vote would have serious implications for foreign direct investment.

He said the policies of austerity, which he said were inherent in the treaty, have sent demand in the economy off a cliff.

Sinn Féin also launched its referendum poster campaign today.

"The choice before the people on 31 May is clear, people must decide if they are for more austerity or for investment in jobs and growth," Sinn Féin President Gerry Adams said at the launch.

"I want to welcome the recent interest in jobs and growth from the Yes side in the referendum campaign. But talking about jobs doesn't get people off the dole.

“To create jobs you have to invest.

"You cannot create jobs by cutting €8.6bn from the domestic economy. Yet this is what Fine Gael and Labour have signed up to. And if we vote Yes to the Austerity Treaty on 31 May we will be signing up to a further €6bn in cuts and tax hikes post 2015.”

Meanwhile, Minister for European Affairs Lucinda Creighton has dismissed suggestions that Ireland could veto the setting up of the European Stability Mechanism.

Ms Creighton said that the ESM only requires the support of countries who will contribute 90% of the fund, and Ireland represents just 1%.

She also questioned why Sinn Féin would want to try stop the ESM.

Ms Creighton also said Sinn Féin were "doing their sums on the back of an envelope" by suggesting the treaty if passed would result in additional cuts of €6bn.

She was speaking at the launch of a Fine Gael website, which advocates a Yes vote in the fiscal treaty.