Cameron at a Tetley factory. Flickr/Number 10. Some rights reserved.The CPS announced this morning it would not be pressing charges against Conservative party candidates over allegations of over-spending and breaking Electoral Commission rules.

The key point from the Electoral Commission statement is this: "In order to bring a charge, it must be proved that a suspect knew the return was inaccurate and acted dishonestly in signing the declaration. Although there is evidence to suggest the returns may have been inaccurate, there is insufficient evidence to prove to the criminal standard that any candidate or agent was dishonest."

In response the Tory chairman Patrick McCloughlin said: "These were politically motivated and unfounded complaints that have wasted police time. We are glad that this matter is finally resolved."

But the complaints weren't unfounded and the matter is not yet resolved. The CPS is still deciding whether to bring charges against the Conservative candidate in South Thanet.

But more broadly, the Conservatives were fined a record £70,000 just a month ago and its former treasurer reported to police after the Electoral Commission found “significant failures” in reporting campaign spending during the 2015 election.

The journalist Paul Mason tweeted: "CPS confirms: UK electoral law unenforcable. While labour movement accounts for every penny, billionaires can buy any election they want"

Indeed, others also pointed to problems within electoral law that made it harder for the investigation to result in prosecutions.

"Election law is separated (for no good reason) between national and local. The @ElectoralCommUK deal with national. Police/CPS, local," tweeted the lawyer David Allen Green. So while the Electoral Commission did take action by levying a big fine, the CPS could not prosecute local candidates as it could not prove they knowingly broke the law.

The Lib Dem leader Tim Farron said the decision had left a "cloud hanging over British politics".

So what explains this confusing situation that many have criticised?

It's the split in election law between local and national spending that has allowed the Conservatives to get away without any charges so far.

Constituency candidates are required to stay within certain spending limits during the 'short' election. Money spent by the national party HQ towards a local election also counts towards that local limit, but only if it mentions the local candidate.

This is why Theresa May has been able to advertise in local newspapers without adding to local spending limits, as she has focused on herself not the local candidate.

But the Conservative did break local spending limits in the 2015 election. However since the national part is handled by the Electoral Commission, not the police, the worst it got was a fine. And since the CPS cannot prove beyond doubt the local candidates or election agents were being dishonest, no charges were pressed.

This episode illustrates the urgency with which electoral law needs to be updated and made more transparent for our democracy to be protected from abuse.