Washington  - The leader of Barack Obama's vice-presidential search team resigned on Wednesday after days of criticism over his ties to the subprime mortgage crisis at the heart of a US economic slowdown.

Jim Johnson was one of three people tasked with screening potential running mates for Obama, who clinched the Democratic presidential nomination last week.

Caroline Kennedy, daughter of slain president John F Kennedy, and Eric Holder, a former deputy attorney general, are the other two involved in the search process.

Johnson led the search team for 2004 Democratic candidate John Kerry, but was recently accused of receiving favourable loans from subprime mortgage lender Countrywide Financial, a company Obama had sharply criticized for its lending practices in the past.

"Jim did not want to distract in any way from the very important task of gathering information about my vice presidential nominee, so he has made a decision to step aside that I accept," Obama said in a statement. (dpa)