A sharp rally for the dollar helped drive oil prices to a six-week low on Tuesday, which in turn helped calm equity investors’ nerves in the wake of some disappointing US earnings reports.

The dollar had fallen to within striking distance of a fresh record low against the euro before rallying on comments by Hank Paulson, the US Treasury Secretary, and Charles Plosser, the president of the Philadelphia Federal Reserve and a member of the Federal Open Market Committee.