Under the double rent deduction rules, a tenant company takes its rent - say £27 per square foot - and doubles it. This is then calculated at the marginal tax rate - £5.40 for those firms paying tax at 10 per cent - and this is deducted from the original rent, leaving the company to pay a net rent of £21.60.

But the savings are far more significant for firms paying tax at higher rates. This includes partnerships, such as law and accountancy firms, and the banks which are currently paying corporation tax at a rate of 28 per cent.

A firm paying tax at 46 per cent would save £24.84 on rent of £27 per square foot, leaving them to pay a net rent of just £2.16 per square foot.

Firms in the IFSC are also exempt from paying rates to Dublin Corporation for 10 years.

At present, businesses elsewhere in the capital pay a rate based on the valuation of the property of £38.80 per £1 valuation which goes into the municipal coffers to pay for the upkeep of the city and the running of local government.