The Scottish Rugby Union said money was not a barrier to securing Vern Cotter as head coach before next year as they revealed the New Zealander could yet be persuaded to leave club rugby this summer.

Mark Dodson, the SRU's chief executive, has defended the decision to appoint Cotter as the permanent successor to Andy Robinson, despite the Clermont Auvergne coach being unable to make the move for another 12 months because of his contract in France.

With that leaving just over a year for the 51-year-old to prepare Scotland for the 2015 World Cup, some have questioned the wisdom of an appointment that will require the recently appointed director of rugby, Scott Johnson, to remain in the interim coach's role he carried out in this year's RBS 6 Nations.

"We always knew Vern wasn't available until 2014, that he was contracted to Clermont until then, but we felt he was the best man for the job," said Dodson. "If he can be persuaded to come earlier than that, and if Clermont are prepared to release him, we will be delighted to have him. But we are banking, we are planning, on the fact that he is going to join us on June 1 [next year]. I don't think it's a financial issue, it's about the way we wanted to do our business – we honour people's contract.

"If you want the very best in the world you sometimes have to wait for them and we believe this is the right man to lead us right through to the next World Cup."

Peter Wright, the former Scotland and Lions prop, is among those who have queried the decision to wait for Cotter. "It is going to be 18 months of an interim coach and I don't think that's right for an international team," said Wright.

"I would have preferred a candidate that would have come in straight away. But the SRU have said they've got the man they wanted and I think he's a good, good coach and I think he's a guy who could take Scottish rugby on . . . I think Johnson will do a good job for the year before Cotter comes in, but he's going to come in with a year to go before the World Cup. Is that enough time to prepare Scotland for the World Cup?"