Rory Stewart has broken down the "insanity" of how government jobs are handed out, saying even fish and chip shops would collapse if they were run in the same way.
Stewart, a Conservative ex-minister himself who ran for prime minister in 2019, has also called for ministers to be given a minimum two years in roles in order to get a proper grip of their jobs.
In the wake of Daniel Khalife's escape from Wandsworth Prison this week, it was pointed out on Sky News's Sunday Morning With Trevor Phillips programme that there have been seven prisons ministers since 2019.
And in his new book, Politics On The Edge, Stewart revealed his own unease at being appointed prisons minister by Theresa May in 2018.
He wrote: "I hadn't spoken to a prisoner or a prison officer in 20 years and I had never met someone who worked in probation. But thanks to the genius of the British ministerial system, I was now responsible for all the prisons, prisoners, ex-offenders, prison officers, probation officers and sentencing policy in England and Wales."
He told Phillips: "I'm obviously attacking myself... I'm trying to show how ignorant I was, and what a disgrace it is that someone like me gets these jobs."
Stewart, who is now better-known as the co-host of the popular The Rest is Politics podcast, said: "It's completely mad.
"As a minister you're trying to put a brave face on things. You're trying to come on programmes like this and defend yourself.
"The truth is, you could not run a fish and chip shop in the way in which the British government is run. It's insane.
"I tried to do a good job, I am sure Alex Chalk [the justice secretary dealing with the fallout of Khalife's escape] is working very, very hard. It's not that politicians are necessarily incompetent or daft, it's that these jobs are mad.
"It cannot make sense to put somebody into a job as important as that for just a few months.
"Look at the number of defence secretaries we've had. Look at the fact Grant Shapps has been through five jobs in the cabinet in just over a year."
Stewart added: "We need governments that say, 'You must remain for a minimum of two years in these jobs unless you have a horrible scandal.' And we need to look to the American system where they have genuine professionals as cabinet ministers."
Shapps was appointed defence secretary last month. He was previously:
transport secretary between July 2019 and September 2022
home secretary – for six days – in October 2022 amid the collapse of the Liz Truss government
business secretary between October 2022 and February 2023
energy security secretary between February 2023 and August 2023
Upon his appointment as defence secretary, Shapps faced questions over the depth of his knowledge.
"Only two of the last 15 defence secretaries have come from the military," he told LBC as he defended his capabilities.
"Its actually highly unusual. We have a civilian government and rightly we put civilians in charge of it. I think that the Ministry of Defence will benefit from having a hugely experienced secretary of state."
Stewart has previously spoken of the "disgraceful" turnover of ministerial jobs, admitting he himself was part of the "charade" by taking new roles.
In 2020, he told BBC Radio 5 Live: "It's a sign we're not a serious country that this happens.
"I remember when I got my first job as environment minister being very excited: 'I'm going to do this for five years, make a real mark. Plant 100 million trees, transform the water system.'
"I began writing a 25-year environment plan and just as I was about to finish, I was moved to be the Middle East and Asia minister."