David Cameron is to base his forthcoming memoirs on a frank and contemporaneous audio diary of his time as prime minister, according to a report.

He recorded 53 hours of conversations with Daniel Finkelstein, the Times columnist and former Conservative adviser who is a close friend of Cameron, and who was made a peer in 2013, Finkelstein’s newspaper said.

The recordings were often made weekly, when the pair met with no others present, sometimes for lunch but usually in the evening at the prime minister’s Downing Street flat.

The chats reportedly covered domestic and international affairs, the way government operated and Cameron’s views of foreign leaders, with Finkelstein pressing Cameron for details he might otherwise later forget.

The conversations were Finkelstein’s idea, the Times said, and based on The Clinton Tapes, which featured recorded interviews and chats with Bill Clinton by the US historian and author Taylor Branch, a friend of Clinton.

Cameron’s audio memories were recorded on the slightly outdated media of the MiniDisc, the report said, supposedly because the technology is seen as almost impossible to hack into. Cameron kept the discs himself.

The interviews reportedly span virtually the entire period of Cameron’s prime ministership, from soon after the 2010 election until just before his resignation after the EU referendum.

The Times said Cameron is “calm and reasonable” in the recordings, adding: “He did not get angry about events but could at times be frank about the individuals with whom he was dealing.”

Even before he decided to step down as an MP last week, Cameron was reported to be planning a quiet period in politics so he could concentrate on writing his memoirs, with publishers invited to submit bids based on a synopsis.

According to one report, Cameron is expected to receive an advance of about £1.5m for the book, notably less than that paid to Tony Blair for his autobiography, A Journey, in part because of Cameron’s lower profile in the US.