The Deputy Chair of the Liberal Democrats has accused Boris Johnson of "extraordinary arrogance" after he announced plans to run for Parliament in 2015.
Sir Malcolm Bruce told ITV News it looked as though the Mayor of London was an "opportunist" who thought he could "walk in and out of Parliament" as he pleased.
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The major party leaders' campaigns for the General Election will remain suspended on Wednesday following the Manchester terror attack.
Thousands of people have donated to help the families of the victims - as well as a homeless man who came to their aid.
Some children, particularly those who have been more directly affected, may show symptoms of stress and trauma.