WINNIPEG -- Manitoba's acting ombudsman will investigate an accusation that the government covered up a damning email in order to protect a minister.

Mel Holley says his office will probe a complaint filed by the Opposition Progressive Conservatives over information that was not released under the province's freedom of information law.

In April 2012, the government invited hundreds of immigrants and immigrant service workers to pack the legislature public gallery for a debate criticizing the federal government.

The Tories said the government was wrong to use civil servants to round up supporters for a political debate and filed a freedom of information request to find out who was behind the plan.

An email that proved then-immigration minister Christine Melnick was behind the idea was initially withheld, but was turned up soon afterward by the ombudsman.

The government has said the email was inadvertently missed, but the Tories say it appears to have been a deliberate attempt to hide information and protect Melnick.