In a letter to members last week, Law Society president Michael Irvine noted that the 1.09 acre site beside the society's existing headquarters was the last undeveloped site on its periphery.

"The opportunity for such an acquisition might never have occurred again, " he said.

Among the attractions of the site, Irvine said, was that it was on the Luas line.

"In the course of a lengthy debate at the Law Society Council, one Council member seemed to sum up the view of most when he said that very few purchasers ever regret buying the site next door, " he wrote to members.

The purchase price paid for the site, which was bought from the McGrath Group, represents a price of 18.57m per acre. Planning permission was already granted on the site for 141 apartments, seven storeys over basement, with 122 carparking spaces, a creche and 431 sq m of retail space.

Law Society director-general Ken Murphy said that the professional body is not planning to turn property developer. "I can assure you of that."

Murphy said that the site, which is zoned for residential, commercial, retail, education and carparking uses, will be used for "purposes to do with the society".

Given that the 20.425m price tag exceeds the Law Society's 2005 income of 2005, solicitors will be asked to cough up to help pay for it through a hike in the price of their practising certificates for the next decade.

ButMurphy said members seemed happy with the deal.

"We have had many letters and emails from many members of the profession, who have been overwhelmingly positive in their support, " he said, adding that "no complaint whatsoever" had been received.