Research by Central Bank economists highlights uncertainty around future growth in the economy and the impact this could have on national debt.

The central assumption in economic planning is that Ireland's debt to GDP ratio will peak next year around 120%.

The new research says such is the uncertainty surrounding economic growth that by 2015 the debt ratio could be down to 95%, if growth is stronger than expected.

But it could also rise to 140% if growth fails to materialise.

The analysis is contained in a note by economists Laura Wymes and Colin Bermingham. It is being published by the Central Bank, but does not reflect the official views of the Bank.

The research examines the impact of the Fiscal Compact on Irish budget planning in the post 2015 period.

Regarding the Balanced Budget rule, it says that from 2016 onward the Government would have to run a primary balance (surplus of income over expenditure before debt service costs) averaging 3.6%, if it is to keep on reducing the deficit by 0.5 percentage points of GDP each year.

At such a pace it would take until 2020 to comply with the Fiscal Treaty requirement of a structural deficit of no more than -0.5% of GDP.

The current Government/Troika plan shows the Government deficit reducing from -8.3% this year to -7.5% next year, -4.9% in 2014 and -3% in 2015.

It says the debt reduction rule (a reduction of 1/20 of the outstanding debt ratio above 60% of GDP) will not become binding until 2019, when the national debt is assumed to have already stabilised and be on a downward trajectory.

However, central banks are becoming more inclined to factor uncertainty into their economic models, reflecting the fact that forecasting the future is virtually impossible, particularly over longer time periods.

The current Government plan is to achieve a small primary surplus in 2014, and then grow it. But that is based on robust growth levels. The Central Bank economists assume nominal GDP growth (i.e. real growth plus inflation) averaging 4.7% in the period 2016 - 2020.

Prior to that the economy is expected to return to strong growth from 2013 onward, and should grow in nominal terms from around €160 billion now to €184 billion by 2015.

However, risk analysis by the Central Bank economists factors in uncertainty about growth prospects. They suggest that in a no-growth environment, GDP in 2015 could be stuck at €162 billion. Or they also say it could have grown strongly and have shot up to €202 billion.

While on current plans and projections Ireland should not have to make any extra effort to meet the terms of the Fiscal Treaty, those projections do rely on pretty strong growth levels, which are by no means assured.