Stewart Jackson believes underestimating Jeremy Corbyn and failing to capture the Muslim vote are to explain for his shock election defeat.
The Conservative politician was ousted as MP for Peterborough by Labour's Fiona Onasanya with some votes needing to be recounted.
Mr Jackson, who has been very outspoken during his 12 year term in Parliament, told the Peterborough Telegraph: "My issue is our manifesto as a party at this General Election was probably a missed opportunity. It wasn't as positive as it could have been.
"I think also there's been a very significant demographic change in Peterborough which has had an impact - particularly we haven't won the support of the Muslim community as evident by the voting figures by ward.
"I think perhaps as a party we underestimated Jeremy Corbyn.
"It's always been a tough seat, it's always been a marginal seat. But I've had a wonderful 12 years. It's been an honour and a privilege to be able to represent the people of Peterborough, and I will still be involved in the city as a local resident, using the public services.
"And I wish Fiona Onasanya all the best in the future. It's a big job, an interesting job, and I'm sure she'll fulfill her role in a superb way."
UKIP did not stand in Peterborough this election due to Mr Jackson being a strident eurosceptic, but the Conservative said not as much of the UKIP vote came his way as he expected.
He is now planning to take a break from politics and start work in a different field.
He added: "I'm going to re-focus my life on different things, support the Conservative Party, and hopefully in the near future do something much more interesting outside of Parliament.
"This is an opportunity to turn a new chapter in my life."
Ms Onasanya, a solicitor and Cambridgeshire county councillor who lives in Paston, said the voters have "sent a very clear message to the Tories. They are not amused at what's been going on and they want change.
"If you want a candidate in Peterborough who will stand up for you and deliver change on your doorstep, you vote for Labour.
"As your MP, I will give you 100 per cent of my attention. I want to hear from you, I want to work with you and let's move Peterborough forward."