British prime minister Theresa May has moved to revive her faltering election campaign with a pledge to embrace “the promise of Brexit”, amid falling poll ratings before next week’s vote that have alarmed her Conservative party.

Mrs May’s lead over the opposition Labour party has fallen from 20 points at the start of the campaign in mid-April to an average of just nine points, according to the Financial Times poll tracker, suggesting that hopes of a Tory landslide to bolster her authority before Brexit talks with the EU are receding.

After losing ground following a Tory proposal, swiftly withdrawn, to make some middle-class families pay heavily for social care, the prime minister returned to her core election theme of Brexit, claiming that only she could deliver a good exit deal and secure a “brighter future” for the country.