Extradition between Ireland and Britain could break down after Brexit, according to a top Irish justice official.

The best-case scenario, laid out in papers from the justice department, is that extradition takes “four of five years” once Britain leaves the EU.

The worst-case scenario, according to James Martin, its head of international policy. is that extradition becomes impossible.

Officials fear a “very significant” deterioration of co-operation between Dublin and London, causing “immediate and serious problems” in dealing with serious criminals if the UK also exits a handful of EU-wide conventions.

Under the European Arrest Warrant (EAW) system, police in any EU country can ask its counterparts in another member state to arrest a criminal suspect and return them for prosecution. The process takes as little