SAN DIEGO (CN) – California Treasurer John Chiang called on the state’s Republican congressional representatives Thursday to vote against the GOP tax plan, which he said would decimate affordable housing in the state and increase homelessness.

Chiang said California – home to a fifth of the nation’s homeless population – stands to lose two programs which have produced two-thirds of the affordable housing units built in the state.

The Tax Cut and Jobs Act proposes eliminating the Private Activity Bond Program and the 4 percent Low Income Housing Tax Credit. The programs created more than 20,000 affordable homes in California in 2016 used to house low-income residents including veterans, seniors, persons with disabilities and those experiencing homelessness.

The programs have helped “those most in need of housing and least able to obtain it on their own,” Chiang said.

“If these to critical programs are eliminated, it will throw gasoline on the statewide housing crisis that is becoming a full-blown humanitarian and public health catastrophe,” Chiang said.

If the tax plan passes, California stands to lose 300,000 affordable housing units over the next 10 years, according to Chiang.

The treasurer pointed to San Diego’s hepatitis A crisis, which has killed 20 people and sickened 544 people, as a manifestation of the shelter crisis in the state. The virus has mostly affected San Diego’s growing homeless population – which increased 14 percent this year – and is being spread by unsanitary conditions, according to the Regional Task Force on the Homeless.

California currently faces a 1.5 million housing unit deficit, a housing shortage gap which grows by 60,000 units a year. The crisis led Gov. Jerry Brown to sign an avalanche of bills this year aimed at quelling the housing crisis, including a $4 billion housing bond which will go before voters next November.

But Chiang said if the GOP tax plan passes, it would effectively “cut us off at the knees” and gut the affordable housing funding mechanisms in California. He said many of the California districts represented by Republican Congress members will be “among the greatest casualties” if the affordable housing programs are eliminated.

The 14 California congressional districts represented by Republicans have benefitted from $2 billion in affordable housing assistance that has funded 101 projects and built more than 9,400 low-income housing units, according to data Chiang released Thursday.

“This is a callus tax plan that would benefit just big corporations and the wealthy at the expense of the state’s most vulnerable citizens,” Chiang said.

Some California Republican members of Congress have already said they would not vote for the Republican tax plan, including Rep. Darrell Issa of Vista, who raised concerns about individual tax cuts hitting his constituents unevenly.

Issa’s district has benefitted from $114 million in bonds and $59 million in tax credits. The programs have built nine affordable housing projects and 612 units in Issa’s district.