The fellow Vote Leave campaigner said the "debate should be forward looking on how to make most of life outside European Union - not re-fighting the referendum".
They tend to focus on a gross figure, rather than a net figure - which takes into account the rebate Britain negotiated in the 1980s, and ways in which European Union money paid into Brussels eventually flows back to the UK. "It would be a fine thing, as many of us have pointed out, if a lot of that money went on the NHS, provided we use that cash injection to modernise and make the most of new technology".
Asked if Boris would resign, Johnson senior said: "It seems perfectly clear to me that Boris would say "look, this is such an important issue, the way we leave, such an important issue i.e. are we going to go on with a transition period which may be two years, may be four years, may be 10 years, or are we going to say No, we voted to leave"?"
Johnson, whose carefully tussled blonde hair and apparent bumbling manner has made him one of Britain's most recognizable politicians, had mentioned the figure again in a Saturday newspaper article that laid out his vision for post-Brexit Britain.
Boris Johnson will be "happy, happy, happy" to quit the Government if Theresa May opts for a soft Brexit, his father Stanley has claimed. Commentators called Johnson's article a "warning shot", as he believes he has been sidelined in the Brexit debate so far.
And as well as angering the Prime Minister and being accused of "backseat driving" by Home Secretary Amber Rudd, he is locked in a bitter row with Britain's stats chief.
Maybe she can use her talks in Canada, her presence at the United Nations in NY and more importantly her speech in Italy to restore order, and convince the many leaders she'll meet this week that she is truly in the driving seat.More news: Criticized by Trump, Iran nuclear deal faces tough scrutiny in United Nations talks
The leader of the Scottish Conservatives Ruth Davidson criticized the timing of the intervention, which takes place hours after yet another terrorist attack in London.
"I think she has a point - I had a very busy weekend dealing with what could have been a awful attack on our public transport", Ms Rudd told Andrew Marr.
She described her colleague as an "irrepressible enthusiast" on Brexit who brought "enthusiasm, energy and sometimes entertainment" to the Cabinet.
The former Cabinet minister also told BBC Radio 4's Today programme it was "much better not to have a transition period".
Johnson's dramatic intervention is clearly meant to win support from Brexit hardliners in the party.
Liberal Democrat leader Sir Vince Cable said: "It's like a school that's completely out of control and the head teacher is sitting in her office paralyzed and impotent".
Asked directly by SkyNew's Kay Burley if he had discussed Boris's chances of becoming Prime Minister, his father replied: "We've got Whatsapp nowadays and Whatsapp has encryption on both ends, I'm glad to say".