The whistleblower who exposed lying Penrith MP Karyn Paluzzano says it will be ''almost impossible'' to find a new job after his bruising experience with the NSW Labor Party.

Tim Horan, whose evidence to the Independent Commission Against Corruption (ICAC), prompted Ms Paluzzano to quit Parliament for rorting parliamentary expenses, told The Sun-Herald that Premier Kristina Keneally's staff had sought to discredit him every step of the way after he came forward.

Describing it as ''the worst four months of my life'', Mr Horan, who conceded that he was partly motivated by revenge when he went to ICAC, is demanding an apology from the Premier before he can put the matter behind him and move on.

Ms Keneally, who refused to stand Ms Paluzzano aside over the allegations, first described Mr Horan's claims as ''vexatious''.

Ms Keneally yesterday refused to apologise to Mr Horan, citing an earlier ICAC ruling that she had not breached protected disclosure laws.

Whistleblower: the Premier owes me apology