Minouche Shafik, deputy governor of the Bank with responsibility for markets and banking, said this morning it was "likely" the rate-setting Monetary Policy Committee (MPC) would need to cut interest rates or extend quantitative easing further in order to avoid an economic crisis.
Shafik, who is seen as a key ally of governor Mark Carney, said despite various indicators showing the UK economy has held up in the three months after the EU referendum: "There is no doubt in my mind that the UK is experiencing a sizeable economic shock in the wake of the referendum.
"Any reduction in openness or need to reallocate resources will necessarily imply a slower rate of potential growth for the economy. Moreover, the reality of the protracted process of withdrawing from the EU means we still know very little about the nature of our future trading arrangements, and this uncertainty is weighing on prospects for business investment."
The Bank of England's Brexit package
In August, the Bank unleashed one of its biggest stimulus packages in its 322-year history, cutting interest rates to a record low of 0.25 per cent and pledging to print £170bn in extra cash to pump up the economy through quantitative easing a new "term funding scheme" of cheap loans for banks.
Turning to the prospect for yet more action in the wake of the referendum, Shafik said: "It seems likely to me that further monetary stimulus will be required at some point in order to help ensure that a slowdown in economic activity doesn't turn into something more pernicious. However, the likely timing of that stimulus wil depend on the continued evolution of the data over the coming weeks and months."
The call for further monetary policy easing puts Shafik at odds with Kristin Forbes, one of the external members of the MPC, who last week said she did not believe the economy would need another interest rate cut.
Shafik also piled pressure on the government to act in response to the UK's vote to leave, echoing comments from Carney that the future of the UK economy was "not the gift" of central banks.
She said: "Monetary policy is just one part of the story alongside government's fiscal and structural policies and the degree of international policy coordination. A good balance between them can put us on a more prosperous and stable path."
Read more: Are government bonds too expensive?
The MPC next meets on 2 November, with markets expecting the Bank to cut interest rates to around 0.1 per cent and hold them there until the end of the decade. However, the Old Lady may be tempted to wait until December, and make a rare shift in policy in a month which does not coincide with the publication of its latest economic projections in the quarterly Inflation Report, due in November.
This would give the Bank an extra six weeks to assess the fallout from the referendum and judge how any policies unveiled in chancellor Philip Hammond's Autumn Statement on 26 November could alter their stance.