Stephen Booth is Research Director for Open Europe.

Stephenphoto The EU ‘referendum lock’ returns to the Commons today, potentially marking the final chance for MPs to make amendments and voice their thoughts on the EU Bill, which is designed to give ordinary people and Parliament greater control over future transfers of power to Brussels. Earlier in the year, Open Europe called for a number of loopholes in the Bill to be tightened up, particularly in the areas of crime, justice and immigration where Ministers currently enjoy unchecked power to opt in to new EU laws without any say for Parliament or the electorate.

The Government gave some ground by pledging to put the decision over whether the UK should remain bound by around 90 or so existing EU crime and policing laws beyond 2014 to a vote in both Houses of Parliament. However, it has remained very vague about giving Parliament or voters more power over whether the UK should sign up to new EU justice and immigration laws. It has promised only to allow proposed laws “where there is particularly strong Parliamentary interest” to be debated. How this would work in practice and who decides the threshold for a ‘particularly strong interest’ remains far from clear.

These issues are unlikely to be revisited in tomorrow’s debate but another hugely important one is: the EU’s accession to the European Convention on Human Rights, which would mean the EU institutions and EU laws could be challenged on human rights grounds at the European Court of Human Rights (ECtHR).

Over the last month we have seen the democratic and economic cost of human rights rulings from both European courts, the Council of Europe’s ECtHR (overturning the ban on prisoners’ votes) and the EU’s European Court of Justice (the introduction of unisex insurance premiums).

At a time when the Conservative Party is reportedly (£) prepared to reconsider the UK’s relationship with the Strasbourg Court, EU accession to the ECtHR is no small matter.

Under the Lisbon Treaty, EU accession to the ECtHR is subject to UK veto but, under the EU Bill as it currently stands, UK agreement would not require an Act of Parliament but only a resolution of approval in each House. Is this really the full and frank democratic debate we should expect on an issue that is clearly of huge political importance?

Once the EU is subject to the jurisdiction of the ECtHR the number of controversial human rights cases will only increase and the confusion over the ultimate jurisdiction over human rights law is likely to create a legal minefield. EU accession to the ECtHR would place the entire body of EU law in the hands of the Strasbourg judges. And if EU law is rewritten to appease the ECtHR, the UK would be bound to implement it under the terms of its EU membership.

The ECJ’s decision to rule that it is illegal for insurers to charge different premiums to male and female drivers, despite the statistical evidence that the former pose a significantly higher risk, is the perfect illustration that EU laws can take on a life of their own in the hands of unaccountable judges. Who knows what creative things the ECtHR would do if it gets its hands on EU law too.

Handing over jurisdiction over EU law, which has to be implemented in the UK, to the Strasbourg court must qualify as a ‘transfer of power’ under the terms of the Bill, even if it is not to Brussels but to Strasbourg.

Conservative MP Chris Heaton-Harris has tabled an amendment that would require any UK Government thinking of approving EU accession to the ECtHR to put the question to a referendum. Given the evidence of recent weeks there can be little argument that this issue is just as worthy of a referendum as many other ‘transfers of power’ addressed in the Bill. So how will the Government respond?