Improper allocation of housing units, misuse of funds and an insufficient supply of land are undermining China's massive affordable housing program, a report by the State Audit Office said on Monday.

The office, which reports to China's cabinet, said 4,428 affordable homes were kept vacant for too long, 4,247 units were allocated to unqualified families, and another 4,407 units were used for purposes other than providing shelter for low-income families.

The State Audit Office released the data as part of implementation of the government's budget in 2010, when it also disclosed local government debt.

Beijing has pledged to build 36 million homes over the next five years at an estimated cost of more than 4 trillion yuan ($619 billion), for low- and middle-income families.

The government accomplished its goal of starting construction of 5.8 million affordable housing units in 2010 and lifted the target to 10 million units this year. But many economists and industry analysts worry that a lack of funding, unfair distribution and poor construction quality will hinder Beijing's ambitious push.

The State Audit Office said its check of affordable housing construction in 16 cities last year also found that 10 local governments had failed to provide as much land as planned and that 90 million yuan from special funds was misused.