Some unscrupulous developers were "gazumping" young people buying new homes and were putting up house prices overnight, the Minister for the Environment, Mr Dempsey, said.
Outlining some of the reasons for the dramatic rise in prices, he said they also included "downright greed " among some builders who were "doing the industry a great disservice and should stop it".
Mr Dempsey said there was a lack of serviced land available and there was no excuse for hoarding it. Criticising builders, he said a number had bought land some years ago for a price well below what they would pay now.
The Minister pledged the Government to building affordable housing for young couples and told delegates that the Government promised 500,000 new houses in 10 years compared to Fine Gael's 328,000 over a 12-year period.
Mr Dempsey's speech followed a debate dominated by concerns about election reform, pollution, roads and the new taxi plates.
A delegate from Tipperary North, Mr Michael Ryan, wondered how many roads would pass a national roads test if it were introduced.
He said that if Irish drivers were expected to have their cars up to the same standard as other European motorists they were entitled to have their roads up to the same standard as the rest of Europe.
The environment workshop which the Minister was addressing passed a motion supporting the Government making taxi plates available to all public service vehicle drivers and that current taxi plate owners in Dublin should be compensated.
A number of speakers were concerned about electoral reform. Mr Bernard Lennon from Tipperary South said that electors would be able to vote anywhere if they had a magnetic strip card which gave their name, address and constituency. They would swipe it through a "reader" and a computer would record it. This he said would enfranchise a further 20 per cent of people, currently unable to vote.
The Minister told him however that he was "at least 10 years ahead" of his time. A number of people would be able to vote electronically at the next election and by the 2004 local elections everyone would be able to vote electronically.
The Minister rejected views that there was no need for electoral reform or a list system. Mr Gerry Callanan from Dublin East said the current system worked well.