If the UK were to leave the EU and EEA, UK competition law is unlikely to be very different in the short term. The Competition Act 1998 is self-standing but is based on EU law and the substantive application of competition law mirrors European law. On this basis the nature of competition law in the UK will remain largely unchanged. However, over time there is the possibility that UK competition law takes a different approach than that which is practised in the EU and EEA. However, EU competition law would still apply to UK companies trading in the EU. Competition law enforcement may also result in parallel investigations in both the UK and EU.

Exit from the EU is likely to end the "one stop shop" merger clearance regime that currently exists. This would require some transactions being notified both at the UK and EU level if they qualify for consideration under both competition regimes. M&A deals that trigger notifications in both the UK and EU means merger filings would potentially become more time consuming, complex and costly to notify and clear.

EU public procurement and state aid rules may no longer apply to the Government but it would still be bound by World Trade Organisation rules on state subsidies.