The free speech provision of the European convention on human rights, Article 10, gives journalists a strong right to protect their confidential sources of information.

Yet the draft investigatory powers bill, published on Wednesday as a replacement for the outdated Regulation of Investigatory Powers Act, fails to guarantee this fundamental human right.

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We should all be worried. Journalists now routinely deal with their sources on smartphones and laptops. Covert access has become a quick and easy way to identify a source.

If sources understand they can be identified in this way they will be reluctant to risk dismissal (or possibly prosecution) to pass on information. We will get fewer stories telling us things that government and big business does not want us to know.

In 1996 the European court of human rights articulated the need for the right to protect confidential sources. It said without such protection “sources may be deterred from assisting the press in informing the public on matters of public interest. As a result the vital public watchdog role of the press may be undermined and the ability … to provide accurate and reliable information may be adversely affected.”

The right has two key elements.

First, the state cannot obtain journalists’ information in order to identify a source unless there is an overriding public interest requiring disclosure. This means an interest that is of greater weight than the public interest in protecting journalists’ sources. Such an interest may arise in a criminal investigation into murder, terrorism or organised crime. But not in a routine police investigation.

Second, there must be no other route by which the state can identify the source. As the Strasbourg court puts it, because of “the importance of the principle at stake, the journalist should be the last, rather than the first, means of arriving at evidence required”.

But it can be very difficult to decide whether there is such an overriding interest. Only a judge can do this properly. And the judge should have the benefit of evidence and argument from the journalist as well as the state. The court of human rights said long ago that in source cases “the full picture should be before the court”.

These considerations mean that covert access should only be used to identify sources in the most exceptional cases. They also indicate that the judge must be free to make his or her own decision, faithfully applying the convention principles. In 2006 the Dutch secret service, the AIVD, recorded calls by two reporters who had published leaked information. It showed the Amsterdam underworld had details of the service’s investigations into organised crime. The AIVD wanted to identify the source in its midst.

In 2012 Strasbourg found violations of the journalists’ source protection rights. The surveillance had not been authorised by a judge “in a position to carry out this weighing of potential risks and respective interests” applying clear criteria reflecting the familiar elements of the source protection right - including whether a “less intrusive measure can suffice…”

The government’s bill has the same flaws.

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Where the police, though not the security services, seek journalists’ “communications data” - the service provider’s record of who they phoned, texted or emailed, from where and when - a judge will at least have to assess whether the police have “reasonable grounds” for the intrusion.

But this is just a review of a police decision, already taken, against a standard that the police will find easy to make out. The judge will not make the decision.

Nor does the bill follow the Strasbourg principles. There is no reference to a right of source protection that can only be displaced by an overriding public interest. Nor must the police exhaust other lines of inquiry. The data can be obtained for any number of reasons, including investigation of any crime, however minor. The judge will only have the police’s side of the case as the journalist will not be told anything. The case for protecting press freedom will not be articulated.

The bill must be amended to give this protection. Or covert powers will become the remedy of choice for the state seeking to identify sources. MPs and peers must act swiftly to prevent this happening or it will be a dark day for our democracy.