Ukip leader Nigel Farage conceded his party had been defeated during the by-election, but hailed the result as Ukip's "strongest ever by-election performance".
Speaking after the result, Mr Farage said: "I think there'll be an awful lot of Conservatives with a majority of less than 10,000 who will look upon this result in sheer horror."
But he admitted he would have liked to have done better in Newark.
"Yes, I mean the majority's halved, but nonetheless for Ukip it's still a good night's work," he said.
More top news
The former England captain said he was "overwhelmed" by the messages he received from football fans after Rebecca died from cancer.
David Cameron said the measure, which will save £4 million by 2020, showed a commitment to his "all in this together" approach.
The party has dropped its opposition to an in/out referendum on EU membership and now supports a vote, acting leader Harriet Harman said.