Celebrity Treasure Island: Sam Wallace, Karl Burnett and Moses Mackay join the island

Karl Burnett as Shorty St fave Nick Harrison. Photo / Supplied

Celebrity Treasure Island has announced three more of its stars who will battle it out in Fiji for a $100,000 grand prize for charity.

The three stars made the announcement on The Hits radio show this morning, revealing that Shortland Street icon Karl Burnett - who played the beloved Nick Harrison on the long-running soap - will compete for St Johns.

Sol3 Mio star Moses Mackay will compete for The Dream Chaser Foundation which supports children and their families facing childhood cancer in New Zealand.

And in a surprise twist, Sam Wallace shocked his co-hosts by announcing he too was going to the island, and will be competing for the Starship Foundation.

Sol3 Mio's Moses Mackay, Shortland Street icon Karl Burnett and The Hits' Sam Wallace. Photo / TVNZ

Sam's addition to the cast poses an interesting competition as the former Breakfast weatherman will face off against Matty McLean, who currently holds the position.

They also have a lot to live up to given current Breakfast host Hayley Holt won the competition in 2007.

Also heading to the island is former Bachelor NZ star Lily McManus and former All Black Zac Guildford, with more stars to be announced on Thursday.

Celebrity Treasure Island is said to be beginning filming this weekend in Fiji.

It will be hosted by Survivor star Matt Chisholm and ZM host Bree Tomasel and will premiere on TVNZ 2 this winter.