Emma Boon of the Taxpayers' Alliance says the findings of the survey that shows more than 3,000 senior council staff are earning more than £100,000, is shocking.
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Run by the NSPCC the helpline allows employees in any sector to raise concerns anonymously.
PM used a speech in Hamburg to say that the UK will not 'pull up the drawbridge and retreat from the world' but Europe must change.
It is set to remain unsettled into Saturday, becoming drier on Sunday.