Nick Clegg is under renewed pressure over his decision to stop new laws giving police and security services powers to monitor internet and email activity.
The Deputy Prime Minister blocked the so-called "snooper's charter" earlier this month but demands for the legislation to be introduced have heightened in the wake of the savage murder of Drummer Lee Rigby.
Among the fiercest critics was one of Mr Clegg's own peers, who accused the Lib Dem leader of bringing the Communications Data Bill to a halt for "purely political" reasons.
Lord Carlile suggested the reforms it contains might have prevented the soldier's death if they had been introduced two years ago and were "very likely" to stop future attacks.
Home Secretary Theresa May indicated earlier yesterday that the plans would be revived and appeared to be gearing up for a fight with Liberal Democrats.