A battle between conservatives and liberals looms in the States over who will drive the country’s law and order policy after the current Attorney General resigned.

Eric Holder has been one of Barack Obama’s closest allies.

The president praised his record on fighting terrorism, crime and protecting voting rights. The US Justice Department has also listed his accomplishments.

Holder has said his biggest regret was failing to tighten gun controls.

“I come to this moment with very mixed emotions. I’m proud of what the men and women of the Department of Justice have accomplished over the last six years, and at the same time, very sad that I will not be a formal part – a formal part – of the great things that this Department and this President will accomplish over the next two (years),” Eric Holder told a joint news conference with the president.

America’s first black chief prosecutor was praised by civil rights groups for his response to the Ferguson riots, ordering a federal investigation into the police shooting of black teenager Michael Brown.

There was also praise from gay rights groups over his defence of same-sex marriage.

But he was also criticised on other matters and he was found to be in contempt of Congress over an investigation into a botched police sting operation.

Holder says he will stay in office until a successor is chosen. Republicans have hinted they may make that task difficult for Obama.