Britain's Prime Minister David Cameron speaks after retaining his parliamentary seat, at a count centre in Witney, Britain May 8, 2015.[Photo/Agencies]

Miliband was widely expected to resign as party leader. The BBC reported he would do so soon.

A majority would mean Cameron no longer needs the Liberal Democrats, with which he has governed since 2010. The centre-left party was crushed, perhaps reduced to single digits after winning 57 seats five years ago.

Among the stunning results, Ed Balls, in line to be finance minister if Labour had won, lost his seat.

Cameron sounded a conciliatory note, especially towards Scotland, likely to be his first immediate headache.

"I want my party - and, I hope, a government I would like to lead - to reclaim a mantle we should never have lost, the mantle of one nation, one United Kingdom," Cameron said.

Sterling gained more than 2 cents against the dollar

to rise above $1.55 for the first time since late February, and looked on track to enjoy its biggest one-day gain against the euro since January 2009.

The FTSE 100 stock index was up 1.45 percent at 6985, approaching a record high set last month.