|One of Browner's main achievements was hashing out a deal with car makers on raising fuel economy standards [EPA]
Barack Obama's chief adviser on energy and climate issues is stepping down, two White House officials have confirmed.
Carol Browner, a former Environmental Protection Agency administrator under former president Bill Clinton, will be leaving the White House at the same time as Republicans in congress prepare to take on the Obama administration over global warming and the government's response to the massive Gulf oil spill.
During her term, Browner successfully helped to negotiate a deal with American car manufacturers to boost federal fuel economy standards and requiring the first-ever greenhouse gas emissions standards for vehicles.
She also pushed for billions of dollars for renewable energy in the economic stimulus bill.
The administration has so far fallen short, however, on its key domestic priority of passing a comprehensive energy and climate bill to place a firm limit on the emission of pollutants blamed for global warming.
Just after the November mid-term elections, which gave Republicans a majority of seats in the House of Representatives, Obama admitted the legislation was dead. Republicans have criticised regulations targeting air pollutants as raising the costs of doing business and therefore costing jobs.
One White House official said Monday that Browner was "confident that the mission of her office will remain critical to the president".
The official, speaking on the condition of anonymity to the AP news agency, said Browner was "pleased" with the clean energy commitment Obama would lay out in his State of the Union address on Tuesday and in his budget request.
It is not immediately clear whether Browner's position will be filled.
Recently, Browner's office came under scrutiny for politicising the response to the massive Gulf oil spill.
The commission set up by Obama to investigate the disaster said that Browner misconstrued the findings of a federal report when she claimed on national television that most of the oil was gone.
A White House statement later said that she misspoke.
Browner's office also has been criticised by the interior department inspector general for editing a department document in a manner that implied scientists supported the administration's decision to place a moratorium on deep water drilling.
The commission found no evidence that the change made was intentional, and Ken Salazar, the interior secretary, later apologised for the misunderstanding.
Browner's resignation comes amid a series of high-profile staff changes in Obama's White House, with Bill Daley being appointed as the new chief of staff, and Robert Gibbs, the press secretary, set to depart.
David Axelrod, a close Obama aide and senior adviser, is leaving the White House to focus on Obama's re-election campaign, and both deputy chiefs of staff are also leaving.
Staff members who are considering a change have been told to make their moves now or plan to stay for the remaining two years of Obama's term to ensure continuity.