The New Zealand rugby union has sanctioned and fined Chiefs loose forward Sione Lauaki for serious misconduct.

Lauaki last month pleaded guilty in Hamilton District Court to a charge of assault stemming from an incident at a Hamilton bar.

Sentencing has been held over until next month, but Lauaki on Tuesday appeared before an NZRU disciplinary hearing.

Lauaki, 28, who was stood down for one match by the Chiefs after the incident, has been sanctioned and fined an undisclosed amount by the NZRU but remained available for his team, who play the Bulls in Hamilton on Friday night.

NZRU professional rugby general manager Neil Sorensen said on Thursday that the hearing substantiated a finding of serious misconduct, under the terms of the Collective Employment Agreement (CEA).

"We take these matters extremely seriously but in this case there were a number of mitigating circumstances and we are comfortable that the incident itself was at the lower end of the scale.

"However, Sione has a history of similar conduct and we have imposed a sanction which reflects that we have treated this matter seriously," Sorensen said.

He said Lauaki had been given a full and final warning, a substantial fine and one-week suspension, already served.

The career of the powerful No.8, who has played 17 tests for New Zealand since 2005, has been marked by errant behaviour off the field.

Last year he underwent an anger management course after appearing in court on a charge of wilful damage. He was arrested on a charge of damaging three windows and a television at an Auckland motel on New Year's Day.

In 2006, he was offered police diversion after admitting to assaulting a Hamilton security officer and later that year he hit a rival player following an argument outside a bar.

Tongan-born Lauaki has been out of favour with the All Blacks selectors since 2008 but has remained a key member of the Chiefs.

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