Two MPs are challenging the Government in the High Court over the introduction of controversial legislation which gives police and security services access to people's phone and internet records.
The judicial review action brought by Conservative former shadow home secretary David Davis and Labour backbencher Tom Watson centres on the Data Retention and Investigatory Powers Act (Dripa).
The Act was rushed through Parliament in three days in July last year with the backing of all three major party leaders.
Backed by civil rights group Liberty, the MPs are seeking a declaration from the court that the Act is not compatible with Article 8 of the European Convention on Human Rights, which guarantees the right to a private life.
In December, Mr Justice Lewis, sitting in London, gave them permission to bring the case.
A full hearing will now take place over two days before Lord Justice Bean and Mr Justice Collins.
The judges will hear argument that Dripa is incompatible with the Human Rights Act and with the EU Charter of Fundamental Rights relating to respect for private and family life and protection of personal data.
Prime Minister David Cameron and the then Deputy Prime Minister Nick Clegg said the accelerated passage of Dripa through Parliament was necessary because of an emergency created by a ruling in April last year by the European Court of Justice, which they said would have the effect of denying police and security services access to vital data about phone and email communications.
They insisted the Act would simply maintain existing powers, which required communications companies to retain data for 12 months for possible investigation, but did not allow police or security agencies to access the content of calls or emails without a warrant.
Emma Norton, legal officer for Liberty, said in a statement: "The executive dominance of Parliament in rushing through this legislation – using a wholly fabricated "emergency" – made a mockery of parliamentary sovereignty and the rule of law, and showed a staggering disregard for the entire population's right to privacy.
"It is thanks to the Human Rights Act that we are able to challenge the Government's actions – the same Government which now seeks to axe that very piece of legislation and, by doing so, curb the British people's ability to do so in future."
Liberty says it does not dispute the role of communications data in solving and preventing crime, "but does not believe that justifies the costly and lengthy mass retention of records of those who are not involved in such investigations".
It is calling for prior judicial authorisation and a requirement that data is only retained as part of investigations into serious crime and to prevent death and injury.