John Howard says he considered stepping aside for treasurer Peter Costello two years ago, News Limited newspapers report.

The former prime minister, who is set to be profiled in a four-part series on the ABC, says a 2006 newspaper report about his 1994 “secret leadership deal” with Costello convinced him to stay on in the top job.

In the so-called Walletgate affair, Howard said revelation of the 1994 deal meant it would look like he was being forced out of office, adding it was not something he could contemplate.

“My position was that, all things being equal, I would go before the next (2007) election,” Howard says in the TV documentary series.

“I never fixed on any symbolic date. I knew that in order to give Peter a fair go it had to be not less than about a year.

“So that either meant right at the beginning of 2007 or it meant around Christmas 2006.”