With pessimism starting to take hold in the Liberal and Nationals ranks, the outspoken Liberal MP for Leichhardt, Warren Entsch said he believed the trio had already made their intentions clear.

Mr Entsch said he believed Bob Katter, Rob Oakeshott and Tony Windsor, all former Nationals, would announce their support for Labor in the coming days.

With Labor and the Coalition both falling short of the 76 seats needed for a majority in the federal House of Representatives, the three MPs will decide who forms government.

''I think they have painted themselves into a corner and their electors will judge them accordingly,'' Mr Entsch said.

He accused Prime Minister Julia Gillard of making unrealistic promises to secure support.

''It seems to me that Julia Gillard will promise anything to get power,'' he said.

''She'll promise them the bloody world, and then when she's in government they'll go feral, and she'll blame them and have that as a reason to go back (to the polls).''

Mr Entsch backed the way Opposition Leader Tony Abbott had handled negotiations with the trio.

''The way Tony is going, I agree with him completely. You only agree to what is achievable,'' he said.

''There were certain things you can go along with, but when you start talking about some of the things (Bob Katter) is talking about, particularly in relation to trade tariffs, there is no point in even offering them because they are not achievable.''