Plaid Cymru wants to offer grants of up to £5,000 to first-time buyers to help them onto the property ladder.
Plaid Cymru says only people living in Wales would be eligible
Plaid said it would encourage people to save for a deposit as it would offer a pound for pound contribution if it formed the Welsh Assembly Government.
It would be the first scheme of its kind in the UK, and Plaid stressed that it would not be means-tested.
But Labour said it was "poorly thought out," and the Conservatives accused Plaid of "flying a kite".
Plaid claimed the number of young people able to buy their own homes in Wales had fallen by nearly 20% over the past 10 years.
The party said there would be no requirement to pay back the £5,000 to the assembly government, if or when the house was sold on, and only people living in Wales would be eligible.
Plaid leader Ieuan Wyn Jones said the problems of first-time buyers were clear when he spent part of the summer walking around Wales.
"The cost of a home is way above the means of many young people because house prices have rocketed whilst average wages in Wales remain relatively low," he added.
"I believe that an assembly grant of £5,000 would enable more young people to get on the housing ladder and I believe that it would be a very attractive plan."
Plaid are looking to include the scheme in their 2007 election manifesto as part of a comprehensive housing strategy to be unveiled later in the year.
According to the party in 2005, there were at least 14,900 first-time buyers in Wales.
If all of these purchasers received £5,000 from the assembly government it could represent a cost of almost £75m in just a year.
Labour Neath AM Gwenda Thomas said the estimated £75m would be taken out of health or education service funding.
"I can think of many other priorities within housing I would target were someone to hand me £75m a year, such as building more houses or using it to revamp existing social housing," she said.
"Plaid Cymru needs to produce a detailed analysis of the Welsh housing market to reassure us that this £75m injected into it annually would not simply cause a dangerous wholesale inflationary increase in prices. "
Welsh Conservatives said they were also looking at ways of helping first-time buyers.
"It's a concern but this sounds like Plaid Cymru are flying a kite. These things are easy to come up with but not so easy to implement," said a Tory spokesman.
A spokesperson for the Welsh Liberal Democrat described the proposals as "an interesting contribution to the debate".
However they suggested that the plans "sound simplistic, half thought through and something of a lawyers charter. For example - how do you define a first time buyer?"