London (Reuters) – The mayor of London plans to spend 250 million pounds ($326 million U.S.) buying land to tackle the city’s affordable housing crisis, which he described on Wednesday as the single biggest barrier to prosperity for Londoners.

The money will be used to buy land to sell to homebuilders, and the proceeds used to purchase additional sites and create a self-replenishing fund, a draft housing strategy said.

“A generation of Londoners are being priced out of our city,” London Mayor Sadiq Khan said in the document.

“Many cannot afford their rent, live in overcrowded conditions, and see buying their own home as a distant dream,” he said.

Housing prices in London have risen 90 percent in a decade, beyond the reach of workers making average wages.

The fresh funds come on top of 3.15 billion pounds ($4.11 billion U.S.) pledged by the government last year to start building 90,000 new affordable homes over the next four years.

An opposition politician dismissed the housing strategy, Khan’s first since he took office in May last year.

“His pledges to maximise land use is at best vague idealism,” Andrew Boff, a Conservative member of the London Assembly, a body elected to hold the mayor’s office to account, said in a statement.

“He has also failed to explain in any detail where he will obtain 250 million pounds to buy up new land.”

But the strategy was welcomed by g15, which represents London’s largest non-profit housing organisations and manages more than 400,000 houses in the city.

“City Hall has a crucial role to play in securing the land needed to build the homes, which is the single biggest challenge to increasing supply,” Paul Hackett, g15’s chairman, said in a statement.

He said g15 is building about a quarter of the new homes in London and “if we can secure enough land to build on, and rally the support of our partners, we can build many more.”

Khan cautioned that solving London’s housing crisis will be “a marathon, not a sprint” and said 50,000 new homes are needed each year.

After a three-month consultation, the final housing strategy is to be published next year.