Peter Costello remains tightlipped about his political future as his publisher admits wanting to keep him under wraps until his memoirs are released in six weeks time.
The former federal treasurer made no comment as he arrived at his electorate office in Melbourne after a holiday in the Pacific, as speculation continues he could challenge Opposition Leader Brendan Nelson for the Liberals' top job.
Publisher Louise Adler, of Melbourne University Press, is delighted with the publicity the speculation is generating.
"One couldn't be in a better position as a book publisher than we are currently," Ms Adler told ABC Radio.
She did not say whether she had advised Mr Costello to maintain the secrecy until the publication date, but said that was standard practice.
"We like to keep all of our authors under wraps until the book's publication. We want to maximise media interest in all of our books - that's the conventional strategy a publisher adopts," she said.
Mr Costello has not spoken publicly about his future since the day after the November 24 election, when he said he was moving to the backbench and working towards a career in commerce.
But continuing bad opinion polls for Dr Nelson and his embarrassing policy backdown on climate change have fuelled speculation Mr Costello is considering a comeback.
He is not expected to make a public announcement until his memoirs are published on September 15.