"We are sick of our players being unsettled whilst they are under contract and we intend to give Leeds a bloody nose," said Hull's chief executive, Stephen Ball. "We have got evidence that they have encouraged the player to break his contract."
Vaikona, aged 21, joined Hull 18 months ago, but caught the eye playing for Tonga during the World Cup last autumn.
"We have done nothing wrong," said the Leeds manager, Hugh McGahan. "We have gone through the correct channels and been told that he is not for sale and that is how the matter stands.
"If he was available, we would be extremely interested."
The Leeds chief executive, Alf Davies, also hit back at a whispering campaign that has suggested that the club is unable to pay its players this month.
"It is a scurrilous rumour and there is no truth in it whatsoever," Davies said. "There are a lot of mischievous people around, but nobody can produce a Leeds player who has not been paid in full."
Leeds also announced yesterday that they were considering legal action against their former All Black centre, Craig Innes, following his decision to join Manly Warringah in Australia.
Wakefield Trinity have signed Lino Foai, the Western Samoan rugby union centre.
There will be a First Division team in the semi-finals of the Silk Cut Challenge Cup, with Hull drawn to play the winners of the Dewsbury versus Widnes tie in the sixth round.
SILK CUT CHALLENGE CUP Quarter-final draw: Halifax or Sheffield v Leeds; Salford v St Helens; Bradford v Wakefield; Hull v Dewsbury or Widnes (Ties to be played 24-25 February).Reuse content