Pakistan Cricket Board (PCB) chairman Najam Sethi has written to the country's new prime minister and former star all-rounder Imran Khan to announce his resignation.

Khan, a World Cup winner in 1992 at the end of a 21-year international career spanning 88 Test matches and 175 ODIs, was elected and sworn in as Pakistan's political leader last week.

After enjoying the support of Khan's two predecessors, Nawaz Sharif and Shahid Khaqan Abbasi, Sethi appears to have accepted he will not receive similar backing from the new PM.

Having been in the role for a year, Sethi took to Twitter on Monday to publish a picture of a letter addressed to Khan, confirming his decision to step down as chairman.

"I was waiting for the new prime minister to take oath before submitting my resignation as PCB chairman, which I have done today. I wish PCB all the best and hope our cricket team goes from strength to strength. Eid Mubarak. Pakistan Zindabad," read Sethi's message accompanying the photo.

"Dear Prime Minister, I was nominated to the board of governors of the Pakistan Cricket Board (as per the Pakistan Cricket Board Constitution of 2014 approved by the ICC and Supreme Court of Pakistan) by ex-Prime Minister Nawaz Sharif from 2014-2017 and then again from 2017-2020 by ex-Prime Minister Shahid Khaqan Abbasi," the letter read.

"I was unanimously elected PCB chairman in August 2017 by all 10 members of the BoG for a three-year term ending in 2020. I believe I have served the cause of cricket diligently.

"You have said on many occasions that you have a vision for Pakistan cricket. Therefore it is only proper that you should assume charge and responsibility for assembling a management team for PCB that enjoys your full confidence and trust.

"In order to facilitate your objectives in the interest of Pakistan cricket, I hereby submit my resignation as chairman of PCB and member of its BoG."