Carmel-based Conseco Inc. faces a shareholder lawsuit by a union pension fund over an earnings restatement the company made 18 months ago.

The Fort Lauderdale, Fla.-based Plumbers and Pipefitters Local Union No. 719 Pension Trust Fund filed suit against Conseco late last week in New York federal court.

In a statement issued today, some of the attorneys representing the union pension fund said Conseco misled investors from August 2005 to March 2008 by failing to disclose that its financial statements were inaccurate, including a $20 million overstatement of the value of shareholders’ stake in the company.

In February 2008, Conseco announced it would restate its financial reports for 2005, 2006 and 2007 after a remediation of its financial-controls systems found significant errors in how it accounted for benefits and liabilities in its specified disease, life and long-term care insurance policies.

A Conseco spokesman was not immediately available for comment.