Hundreds of thousands of mortgage holders are set lose a key tax relief on their monthly repayments.

According to figures provided by Minister for Finance Michael Noonan, some 325,000 mortgage holders will lose the relief, which is €850 per annum on average, when it is phased out by the end of 2017.

The relief on mortgage interest expired in 2009 for people who started paying their mortgage in 2003 or earlier, while those who took out a mortage between January 2004 and the end of december 2012 the entitlement for relief ends on December 31st, 2017. Mortgages taken out after December 31st, 2012 do not qualify for mortgage interest relief. It is estimated the scheme will cost the Exchequer €275 million this year.

Fianna Fáil Finance spokesperson Michael McGrath, who obtained the figures, said: "This payment is a very important support for families particularly those struggling with sky high variable mortgage rates.

“The process of withdrawing it from existing homeowners at the same time as they are subject to a residential property tax highlights a Government that is pursuing policies that are making home ownership increasingly unaffordable for families,” he added.

The figures show 349,500 mortgage accounts were in receipt of mortgage interest relief in 2010 while 323,500 are in receipt this year so far.