It looks as if the UK is an unreliable partner of the EU. This is already the case before Brexit, so what wil happen after…
The most recent scandal was revealed on 14 January by The Guardian: Revealed: UK concealed failure to alert EU over 75,000 criminal convictions. Dutch MEP Sophie in ’t Veld is angry about the UK behaviour.

Failure to alert:

The Guardian: “UK concealed failure to alert EU over 75,000 criminal convictions”. Yet another scandal that casts a very dark shadow over security and law enforcement cooperation. The UK gvt has to consider very carefully how it intends to restore trust https://t.co/WPD65YRgO4

— Sophie in ’t Veld (@SophieintVeld) January 14, 2020

Schengen database:

La Grande-Bretagne fait face à la chaleur de l’utilisation «illégale» des données de migration de l’UE https://t.co/41eoaGLZpn

— Sophie in ’t Veld (@SophieintVeld) January 9, 2020

UK accused of ‘behaving like cowboys’ over EU database copying https://t.co/KppkHfSGE6

— The Guardian (@guardian) January 9, 2020

The UK government is behaving like a bunch of cowboys with its illegal use of the #Schengen Information System.

If this deliberate violation is not immediately addressed by @EU_commission, the UK will need to be disconnected from Schengen data after Brexit🚫

— Sophie in ’t Veld (@SophieintVeld) January 9, 2020

Sophie In’t Veld reading from the report I leaked (https://t.co/6XddKhB1eZ )on UK abusing the Schengen Information System. “No more access to the Schengen information system, full stop,” she says. @EUComission refuses to respond. MEPs furious. @SophieintVeld

— Nikolaj Nielsen (@NikolajNielsen) January 9, 2020

Data protection worries:

Will European personal data be safe in the UK? Or will UK be a backdoor to US authorities? Jumping the Brexit gun, the UK already agreed Oct19 to give US authorities direct access to data bases in the UK. Colleague @moritzkoerner and I ask @dreynders and @EDPB Read our letter👇📃 pic.twitter.com/XpBb6EPjWv

— Sophie in ’t Veld (@SophieintVeld) January 13, 2020

More information:

• Revealed: UK concealed failure to alert EU over 75,000 criminal convictions, The Guardian 14 January 2020.
• UK accused of ‘behaving like cowboys’ over EU database copying, The Guardian 9 January 2020.
• Breton’s firm hosted unlawful copy of EU police data, 4 November 2019
• UK taking ‘steps’ after illegal copying of EU Schengen data, EUObserver 25 July 2019.
• UK unlawfully copying data from EU police system, 28 May 2018, EUObserver

Addition 14 December 2020
New article: UK access to EU police database hangs in balance, EUObserver 8 December 2020. Subtitle: “The UK may lose access to the EU’s police database“.