Tas leadership challenge coming, Libs say SPECULATION over the leadership of Tasmanian Premier Lara Giddings has re-emerged, with the Liberal opposition saying senior minister David O'Byrne is preparing a challenge. Deputy Liberal leader Jeremy Rockliff says a call by Young Labor for Greens leader Nick McKim to be sacked from cabinet represents an attempt to destabilise Ms Giddings' leadership. The state's Labor youth wing says Mr McKim, who is Tasmania's minister for sustainable transport, should be sacked over his handling of a six-week industrial dispute involving bus drivers. Mr McKim is one of two Greens ministers in Ms Giddings' ALP-Greens power-sharing government. "Young Labor is doing the bidding of the factional heavyweights, the leadership of the Labor Party, most notably those supporting David O'Byrne," Mr Rockliff told reporters in Launceston on Thursday. Mr Rockliff said Mr O'Byrne had been preparing a challenge with volunteers phoning more than 3000 voters in the minister's electorate. "They're a divided, dysfunctional rabble and David O'Byrne would not be doing this polling if he wasn't very concerned and dissatisfied with the leadership of Premier Lara Giddings," Mr Rockliff said. Mr O'Byrne said he was merely asking voters their opinions on issues and was not polling, ABC radio reported. He was previously forced to rule out a leadership tilt in December 2011. The ALP is languishing in the polls, with Ms Giddings' rating as preferred premier consistently in the low to mid 20s. Mr McKim has refused to intervene in the bus drivers' pay dispute, which resulted in stand-downs on Wednesday, arguing it is a matter between employees and the state-owned transport company Metro. Mr O'Byrne, a former union boss, disagreed with the shut-out, along with several other state Labor MPs and federal member Julie Collins. The talk has fuelled speculation of a cabinet split over the issue, with the Liberals suggesting Ms Giddings has sided with her Greens colleague Mr McKim. Mr McKim has denied there is tension in cabinet over the issue. However, former Labor premier Paul Lennon was installed as a mediator in the bus dispute on Thursday, apparently without Mr McKim's knowledge. Mr Lennon and Mr McKim are old foes in the battle over the pulp mill proposed for northern Tasmania by fallen timber giant Gunns. The Greens minister said he would welcome a facilitator respected by both sides in the dispute.