Former Home Secretary Alan Johnson has said he is in complete agreement with Theresa May on the need to pass the Communications Data Bill before the general election.
He told the BBC's Andrew Marr Show: "We need to get this on the statute book before the next general election and I think it is absolutely crucial.
"Indeed I think it is a resignation issue for a Home Secretary if the Cabinet do not support her in this central part of what the security services do."
The Communications Data Bill - dubbed the "snooper's charter" by its opponents - would give security forces greater powers to monitor communications such as emails.
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