Australia’s World Cup group rivals Wales have been been hit by a major setback after assistant coach Rob Howley was sent home from the tournament over a possible breach of betting rules.

The former Wales captain, who has been part of Warren Gatland’s coaching team since 2008, has departed the squad’s base in Japan just six days before their opening match, the Welsh Rugby Union confirmed in a statement on Tuesday.

The 48-year-old missed Wales’ welcoming ceremony in Kitakyushu on Monday and will be replaced by former fly-half Stephen Jones, the WRU added.

“The WRU can confirm that Rob Howley has returned to Wales to assist with an investigation in relation to a potential breach of World Rugby regulation 6, specifically betting on rugby union,” the nation’s governing body said in a statement.

“The decision was taken to act immediately in light of recent information passed to the WRU.

“No further details can be provided at this stage as this would prejudice the investigation. If required an independent panel will be appointed to hear the case.”

Wales start their Pool D campaign against Georgia on Monday before face the Wallabies in Tokyo on September 29.

The WRU says Howley has “co-operated fully with our initial discussions” but adds that “if required, an independent panel will be appointed to hear the case.”

Howley had been due to leave his Wales coaching role after the World Cup, along with Gatland and fellow assistants Shaun Edwards and Robin McBryde.

Howley enjoyed a glittering playing career, winning 59 caps for Wales and captaining his country on 22 occasions, while also helping Wasps to be crowned European champions in 2004.

He played for the British and Irish Lions in 1997 and 2001, and was part of the Lions coaching staff on their last three tours.