'I defy anyone to produce one single act or law of the EU and the European Court that has actually benefited Britain', the challenge was issued by Peter Hill, the editor of the Daily Express, in the opening pages of the Express' recent EU special edition.

This is the courageous claim that heads off the paper's 'crusade' to end Britain's membership of the European Union. It is not for us to take up the editor's challenge, but with commentators and columnists within the supplement itself variously claiming that 60, 72 and 75 per cent of our laws are made in Brussels, Full Fact wondered just how many EU-induced laws that challenge might cover.

'We now find ourselves under a dictatorship with some 72 per cent of our laws being created by Brussels', claimed Winston McKenzie, the UKIP spokesman for Culture, Media and Sport in one article in the 'Get Britain Out of the EU' supplement. Meanwhile UKIP leader, Nigel Farage, favoured 75 per cent in his column. This second figure is commonly quoted in UKIP literature and actually originates from a speech given by the former President of the European Parliament, Hans-Gert Pottering: 'if we were not that influential then we would not be the legislator of 75 per cent of all laws in Europe'. Members of UKIP take this as an admission that 75 per cent of all EU member states' laws are made in Brussels.

As many have already pointed out, this quote has been taken out of context and has now gained currency as a valid estimate of the EU's legislative influence in the UK amongst Eurosceptics. In fact Pottering was making a claim for the legislative power of the European Parliament with regard to laws made in the EU and not those made by individual Member States. Even if he had been talking about the European Parliament's influence in individual countries, the estimate would not provide a particularly nuanced interpretation of the EU's influence in the UK.

A recent House of Commons library report notes that it 'remains virtually impossible to give an accurate answer to the question about the number of national measures based on EU requirements'. Their own report suggests that between 1997 and 2009 6.8% of primary legislation (statutes) and 14.1% of secondary legislation (statutory instruments) have had a 'role in implementing EU obligations'. The report also cites other studies which counted the share of domestic laws and regulations resulting from European directives and formulated similar estimates ranging between 10 and 20%.

However, 'legislation' can refer to regulations, as well as directives and decisions. As the authors note, many EU regulations affect quasi-legislative measures, administrative rules, regulations or procedures which do not pass through Parliament. Furthermore, Christensen has also identified a number of “more subtle ways in which the EU may affect national governments' decision making”, for example by adapting their administrative regimes in anticipation of future EU policies. In light of this, the House of Commons concludes that it is 'possible to justify any measure between 15% and 50% or thereabouts, depending on the approach'.

Eurosceptic think-tank Open Europe plumped for a figure that pushed the limits of this scale when it published a report in 2009 that put the average annual proportion of the absolute number of regulations from the EU at 50.4% between 1998 and 2008. This figure was calculated based on regulations that were likely to have an economic impact on business, the public sector and the third sector.

There are wild divergences in the estimates but the lack of consensus is perhaps understandable considering the taxonomical difficulties of determining what is and is not an EU-induced law. For example, if a lengthy statute contained one insert from the EU would it be classified as an “EU law”? The library report also suggests that it would be fair to assume that some of the laws that are influenced by EU legislation might have been implemented by the Government anyway.

Ultimately, estimates for the proportion of our laws that come from the EU give little insight into the extent of EU influence and power in the UK since they arbitrarily equate one law with another. With regard to the 75 per cent claim, based on a quote taken out of context, it has little validity as an estimation of the EU's influence.