May promises review into counter-terror bulk data powers
Theresa May has agreed to establish an independent review to examine the operational case for powers which allow for the bulk collection of data.
The home secretary made the offer in a letter to Labour's Andy Burnham.
The independent reviewer of terrorism legislation has agreed to lead the review, reporting over the summer.
David Anderson will assess the powers designed to allow intelligence agencies to harvest large amounts of data from emails and other communications.
This, which is done to try and pinpoint intelligence about terrorists, has been likened to searching for a needle in a haystack.
The home secretary has offered to set up the review in a letter to the shadow home secretary Andy Burnham who has demanded a series of amendments to the Investigatory Powers Bill, often known as the snoopers' charter.
The government needs Labour to support - or at least not vote down - the bill to ensure it reaches the statute book by the end of the year.
The current laws governing the collection of data, enshrined in the Data Retention and Investigatory Powers Act of 2014, are due to expire at the end of this year.
The move by the home secretary follows a recommendation by parliament's Joint Committee on the Draft Investigatory Powers Bill. In a report in February the committee, chaired by the former Labour Northern Ireland secretary Lord Murphy of Torfaen, called on the government to publish "publish a fuller justification for each of the bulk powers".
The committee highlighted three types of bulk powers in the bill for the security and intelligence agencies: the bulk interception of data, bulk acquisition of communications data and bulk interference with equipment.
The independent review will be established under David Anderson once he has selected two experts with security clearance to support him on technical and legal issues. He will report by the summer in time for the committee stage of the bill in the House of Lords.
Mr Burnham described the home secretary's letter as "extremely encouraging" but made clear the government needs to go further to win Labour support. The shadow home secretary was due to tell MPs in the commons debate on the Queen's speech: "A few weeks ago, I wrote to the Home Secretary setting out seven areas where we want to see significant movement.
"Yesterday the Home Secretary wrote to me on two of these issues and I have to say I found her letter extremely encouraging.
"Her commitment to an independent review of the case for bulk powers is a major concession but the right thing to do and something which will build trust in this process."
Mr Burnham welcomed a second concession in the home secretary's letter - amending the bill to make clear that the security and intelligence agencies cannot use the powers to monitor legitimate trade union activity. The government believes that the agencies are not allowed to carry out such investigations.
But the home secretary is happy to amend the bill to reassure her Labour opposite number who supports the Shrewsbury 24 campaign which is pushing for the quashing of the convictions from the 1970s of construction worker pickets, including the actor Ricky Tomlinson. Mr Burnham says the intelligence agencies monitored trade unions in that period.
But the shadow home secretary said he is not yet prepared to offer his support for the bill. He is due to tell MPs: "As the Home Secretary knows, we share her goal of putting an updated law into the Statue Book governing the use of investigatory powers and giving the Police and the security services the powers to do their job in the digital age.
"But we do continue to have serious concerns about the Bill as currently drafted. It does not yet contain sufficiently strong safeguards and human rights protections."
A Home Office spokesperson said: "The Home Secretary has always been clear she will listen to the constructive views of politicians from all sides of the House to ensure the passage of this important Bill. The Government will be bringing forward amendments at Report Stage."