London mayor Boris Johnson has said he will look for a seat to run for Parliament in 2015 "in all probability".
ITV News Deputy Political Editor Chris Ship is following developments.
NEW: Boris says "in all probability I will try to find somewhere to stand in 2015"
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Shadow chancellor John McDonnell has backed a free vote for MPs on the issue.
Savers into the new scheme can expect rates as high as 4 per cent from some banks.