* Party of prime minister demands resignation of senator
* Northern League members insist comments not racist
* Italy's first black minister says receives death threats
Italian Prime Minister Enrico Letta demanded the opposition Northern League party take action after "shameful" racist comments by its members about Italy's first black minister.
Senior League figure Roberto Calderoli, vice president of the Senate, told a political rally at the weekend that Integration Minister Cecile Kyenge had "the features of an orangutan", prompting widespread calls his resignation.
Letta said the comments had damaged Italy's standing abroad and called on the League to "close this disgraceful page once and for all". His centre-left Democratic Party staged a protest in Rome to demand Calderoli's dismissal.
Calderoli, a former minister under premier Silvio Berlusconi with a long history of provocative statements on issues such as Islam and immigration, offered a grudging apology.
"There was nothing racist about it. I didn't even mean to be offensive," he told the daily La Repubblica. "I'm always comparing people to animals."
He dismissed suggestions he should resign from parliament and suggested that Kyenge was not qualified for her job. "I wonder that someone who speaks Italian with difficulty should have been chosen as a minister," he said.
Last month, a local Northern League official posted a Facebook entry saying Kyenge should be raped.
Letta called on the head of the Northern League Roberto Maroni, governor of the regional Lombardy government where the League has staunch support, to rein in members of his party.
"It's not possible that events go on like this," he told a news conference. "Stop it, end it, enough of this shame."
Kyenge, an eye doctor, is an Italian citizen born in the Democratic Republic of Congo who has pushed to change Italy's nationality laws to make it easier for the children of immigrants born there to gain citizenship.
She has been repeatedly subjected to racial slurs since her appointment in April, and said she received threats daily.
"Letters, emails, phone calls. The most terrible are online, including death threats," she told newspaper Corriere della Sera, adding that police had escorted her from one event after someone was discovered waiting to ambush her.
"I always have to be alert," she said.
The Northern League - an important coalition partner in the Berlusconi governments of the past - issued a statement brushing off calls for Calderoli to resign and announced a rally of its own in September against illegal immigration.
Struggling to recover from a series of financial scandals, the League's vote was down by half at February's general election from its showing in recent years, to just above 4 percent, but its members have kept up anti-immigrant rhetoric.
Former senator Erminio Boso said last week he was happy when a boat of immigrants trying to reach Italy sinks.