On Sept. 23, Kwarteng made his first fiscal announcement including a controversial plan to scrap Britain's top income tax rate for the highest earners, part of a package of measures he said would speed up sluggish economic growth.
Last week, a rebellion within the ruling Conservative Party forced Kwarteng and Truss to drop the idea of scrapping the 45% top rate of tax.
"If Kwarteng decides to lecture back, let alone publicly dissent from the G7 consensus, then things will go very badly for him," Posen, a former BoE rate-setter, said.
The BoE said on Monday it was taking further steps to ensure the emergency bond-buying scheme concludes smoothly on Friday.
Register now for FREE unlimited access to Reuters.com RegisterAdditional reporting by Howard Schneider in Washington Writing by William Schomberg Editing by Catherine EvansOur Standards: The Thomson Reuters Trust Principles.