By Teresa Cespedes

LIMA, Peru (Reuters) - Peruvian President Ollanta Humala's approval rating in March dove back down to the lowest levels of his presidency, stung by a political crisis and amid discontent over income distribution, a poll showed on Sunday.

Humala's popularity shed 8 percentage points to fall to 25 percent, according to the Ipsos Peru poll

published in newspaper El Comercio. His approval rate had risen from 25 percent in December to 33 percent in February, buoyed by an international court's ruling on a maritime dispute with neighboring Chile.

But the boost appears to have been short-lived, and Humala's slumping popularity comes at a particularly thorny moment for the leader who took power in 2011.

Congress failed to ratify his new Cabinet on Friday as some lawmakers complained it reflected meddling by powerful first lady Nadine Heredia in the government, creating a major political crisis and effectively leaving the government in limbo. Humala has urged Congress to approve his new ministers when it meets again on Monday.

First lady Heredia also suffered a sharp tumble in popularity, slipping to 27 percent in March from February's 40 percent, which Ipsos linked to her role in the resignation of former prime minister Cesar Villanueva.

The majority of Peruvians do not think Heredia has a positive influence on her husband and would rather she abstain from involving herself in governance, the poll showed.

Many of the poor who backed Humala, a former left-leaning nationalist, are also upset at his swerve to the right and are clamoring for fairer distribution of the spoils of a mining boom.

The poll of 1,206 people was conducted between March 11 and March 14 and has a margin of error of 2.8 percentage points.

(Writing by Alexandra Ulmer; editing by Matthew Lewis)