A Downing Street spokesperson said:
The Prime Minister regrets that Baroness Warsi has decided to stand down and is grateful for the excellent work that she has done both as a Minister and in Opposition.
Our policy has always been consistently clear - the situation in Gaza is intolerable and we've urged both sides to agree to an immediate and unconditional ceasefire.
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The text-to-register service allows mobile users to add their number to the Telephone Preference Service 'do not call' database.