Failure to opt back in to EU criminal justice measures will hamper the UK’s ability to prosecute cross-border crime, making procedures ‘uncertain, cumbersome and fragmented’, the director of public prosecutions told peers today.

Keir Starmer QC also revealed that there was no formal consultation with the Crown Prosecution Service before the government indicated its decision to exercise the block opt-out negotiated by the previous government under the 2009 Lisbon Treaty.

However, he said he was being given the opportunity to express his views now.

Starmer said that some of the 130 measures under threat are of ‘real importance’ to UK prosecutors, who have made wide use of them. In particular, he said prosecutors benefited from the Eurojust hub which co-ordinates prosecutors across the EU; joint investigation teams; the ability to access information on previous convictions and the European arrest warrant (EAW).

All enable serious crimes to be dealt with in a timely manner, he said.

Failure to opt back in to the measures, he said, would mean reverting to bilateral arrangements with individual states, creating an ‘uncertain, cumbersome and fragmented’ approach that is likely to have an impact on the prosecution of crime in England and Wales.

Starmer accepted that there were flaws with the EAW, which critics suggest does not sufficiently protect British citizens and burdens the police with trivial or stale requests, but he said those problems would not be resolved by withdrawing.

In 2001, the year before EAWs were introduced, Starmer said there were 144 extradition requests made to the UK, and the UK sought the surrender of 87 suspects. By 2010/11 that number had grown, with 1,400 requests made to the UK and 1,170 surrenders.

Under the old arrangements, which Starmer said were ‘slow and cumbersome’, it took, on average, a year to get a suspect back to the UK and six years to extradite someone from Britain. He cited the case of the Paris Metro bomber, Rachid Ramda, whose extradition took 10 years. With the EAW, he said it takes on average 63 days from first hearing to final order, including appeals.

In addition, Starmer said that many EU states had removed laws underpinning extradition from their domestic legislation following the introduction of the EAW and would have to create new laws to reproduce the mechanism. This he said could leave a gap that meant extraditions could not occur, delaying prosecutions.

The Eurojust hub, said Starmer, operates at a ‘modest cost’ of £360,000 a year and had assisted the UK in positive outcomes in many serious cases, including rape, drug importation, and cases concerning animal rights extremists. Without it, he said, there would be greater costs and ‘haphazard lines of communication’ throughout investigations.

EU joint-investigation teams, he said, enable swift cross-border co-ordination and allow all prosecutors involved to see all available evidence from the outset, which reduces the scope for admissibility arguments down the line. They have, he said, also led to many successful prosecutions in the UK, saving considerable amounts of money.

Removing the UK’s ability to access information about suspects’ previous convictions, said Starmer, could have serious consequences when it comes to bail decisions, bad character evidence at trial and sentencing.

In the worst-case scenario, he said it could men that a murderer or rapist is released on bail and goes on to commit another offence, because their antecedence was not known to the UK court.

Starmer was giving evidence to a joint inquiry by Lords EU sub-committees into the UK’s possible opt-out from 130 EU police and criminal justice measures in 2014. The committee will hear evidence from lord chancellor Chris Grayling and home secretary Teresa May on 14 February. It aims to report at the end of April.