First of all, why is Labour maintaining an independent central bank? This feature, which is an absolute mark of right-wing neoliberal thinking, and which is a legacy of the Gordon Brown / Ed Balls era from which I would have thought John McDonnell was keen to disassociate himself, has three incredibly unfortunate consequences in that it removes economic policy from democratic control, puts bankers in charge, and makes monetary policy the focus of attention when fiscal policy has to be the future direction of all economic policy. The time for economic policy to come back solely under the control of elected politicians within the Treasury has arrived: it is deeply disappointing to see that Labour has not embraced this idea.
Monetary policy isn’t effective therefore government must, democratically, control monetary policy.
Monetary policy isn’t effective therefore we cannot have an independent central bank controlling monetary policy.
Only fiscal policy is effective therefore government must control monetary policy otherwise they’d not be able to use the fiscal policy they already control.
The true logic is that The Tater desires control of monetary policy because he knows a) that it works and b) an independent central bank would use it to offset fiscal policy.