An Illinois man is suing a marriage guidance counsellor for having an affair with his wife.

Scott Buetow, 35, of McHenry County, had hired the therapist to improve his marriage, reports the Chicago Sun-Times.

But he claims that instead Dan Blair began an affair with his wife that caused the couple to divorce.

His lawsuit seeks more than �100,000 in damages from Mr Blair and the counselling centre where he works.

"He [Blair] had an obligation to provide services, and he willfully abused that for his own benefit," said attorney Hans Mast, who represents Mr Buetow.

Mr Buetow and his wife began seeing the counselor in April 2004 to 'strengthen and stabilise' their 10-year marriage.

While providing both joint counseling and individual therapy sessions, Blair allegedly started a secret romantic relationship with Buetow's wife.

Buetow filed the suit because he believes "he got a raw deal from the person he trusted and confided in," Mast said.

Buetow and his 36-year-old wife, who have four children, were granted a divorce earlier this year.