There was a sneakily released Home Office press release in the early hours of last Saturday:

Police trial new Home Office mobile fingerprint technology
New mobile fingerprinting technology will allow frontline officers across the country to use their smartphones to identify people in less than a minute …

Needless to say Liberty are up in arms as there is no parliamentary oversight nor any proper public consultation.
Anyone who is stopped and fingerprinted on the street (and anyone could be at the whim of PC Plod) will have no opportunity to seek legal advice beforehand, there does not seem to be any discussion of consent, nor is there any indication of whether the information obtained will be retained and if so for how long or for what.
PC Plod is all too good at being ham-fisted and over-zealous with such initiatives, which is why it is important there should be oversight and consultation.
I find this especially disturbing as there is no scientific basis for the certainty with which fingerprints are used for identification. See, for example, this October 2017 article from Science Daily which reports this scientific examination.
As Liberty’s blog post says:

If you have been affected by these new measures, please tell Liberty about it and get legal advice quickly.