An electoral worker with a Scottish Saltire painted on her finger nails counts ballots after polls closed in Britain's general election at a counting centre in Aberdeen, Scotland, May 7, 2015. [Photo/Agencies]

Even if the centre-left party got together with the left-leaning Scottish nationalists and the Greens the exit poll suggested it would still be well short of the 326 seats needed for a majority in parliament.

Miliband, who was widely perceived to have performed better in the campaign than expected, would be likely to come under pressure to step down as leader.

The country's mostly right-wing press has long criticised him for being socially-awkward and presiding over what it has described as a dangerous lurch to the left.

Cameron has pledged to eliminate Britain's budget deficit, now running at 5 percent of gross domestic product, by 2018/19, including through cuts to welfare spending of 12 billion pounds ($18.3 billion). 555 pounds)