...am I to infer that this would result in an extra tax bill?
Yes, that's how I read it. However, lots of agencies are urging caution and there seems to be something of a battle going on within the treasury as to which "bright ideas" get implimented. This article appears to be lobbying against Alexander. Mind you, the alternative looks equally as bad, but maybe only if you get promoted:
The Government has other options if it wants to cut the amount of money lost to the public purse through tax relief on pensions. It is thought that, instead of abolishing 40pc relief, the Chancellor may restrict how much savers can put in a pension each year.
Currently people can save up to £50,000 tax-free into a pension, but it is understood the Government is considering reducing this annual allowance to £40,000 or £30,000 instead. This could also result in a tax bill for highly paid workers in the public sector.