DUBLIN — Ireland’s justice minister resigned in a surprise blow to the country’s 3-year-old coalition government, after a state-ordered investigation concluded that he mishandled the complaints of a police corruption whistleblower.

Alan Shatter said in a letter Wednesday he was quitting to ease criticism of the government when the 300-page report is published within weeks.

Prime Minister Enda Kenny, who received the report Tuesday night, said he regretted Shatter’s resignation, but said the report had found that Shatter responded inadequately to complaints of police corruption made by a serving officer, Maurice McCabe.

Ireland’s police commander, Martin Callinan, resigned in March over the same scandal.

Shatter was regarded as Kenny’s most intelligent, hard-working and reform-minded minister, but as also having a holier-than-thou manner and being unapologetic.

Anti-Semitic material and an unidentified white powder were sent to Shatter earlier this year.

The Irish Army’s bomb squad was sent in April to the Dublin home of Shatter, who is Jewish, to remove the package. The white powder was discovered to be harmless.

The anti-Semitic material was identified in some reports as a swastika or a photograph of Nazi storm troopers carrying flags bearing swastikas.

Prime Minister Kenny told the Dali, or lower house of the Irish Parliament, that the incident was a “new low” for the country. A similar package also was sent to the Department of Justice, he said.

“It’s not in order that that sort of anti-Semitic material is being received by somebody who happens to belong to a particular religion in our country, irrespective of the challenges that we have here,” Kenny said.