Ukip's win in Clacton and massive boost in support in the Heywood and Middleton byelection is "a wake up call" to the Tories, Conservative Party chairman Grant Shapps said.
He told Good Morning Britain that Ukip had taken votes from all parties, but had "cost Conservatives seats in Parliament," putting Ed Miliband closer to Number 10.
Defeated Conservative candidate Giles Watling has pledged to take on Douglas Carswell again at the General Election.
Despite taking less that a quarter of the votes in the Clacton by-election, Mr Watling promised he would be back.
Mr Watling, an actor who starred in the comedy series Bread, declared in his post-declaration speech: "I intend to stand here next May at the General Election when this country will face a clear choice about who they want to be the leader, David Cameron or Ed Miliband."
Conservative Party chairman Grant Shapps has said the Clacton byelection result "shows if you vote Labour you get Ukip.
Grant Shapps: "In his conference speech [the PM said] that you vote for Farage, you got to bed with Farage and wake up with Ed Miliband."
Shapps told Good Morning Britain the UK "will face a massive choice" at the General Election next year.
"It's the most significant General Election for generations," he added.
As Ukip prepares to enter Parliament for the first time, leader Nigel Farage reflects on his party's byelection successes.Read the full story ›
UKIP leader Nigel Farage says there could be more defections to his party in the coming months following Douglas Carswell's thumping victory in the Clacton by-election.
Speaking outside the count, Mr Farage said: "We're the only party that can get big votes shares in Tory heartlands and Labour heartlands. No other parties crosses those old divides of left and right."
Ukip has its first elected MP after Douglas Carswell took almost 60% of the vote in the Clacton by-election.Read the full story ›
Douglas Carswell has told ITV News Political Correspondent Emma Hutchinson that his victory in Clacton was "beyond anything I expected."
Clearly emotional, he said: "I expected to do respectably but wasn't sure I could win. I certainly didn't expect to get more than 50% of the vote. I'm a little bit dazed and humbled. I'm a little bit wow."
In his acceptance speech Douglas Carswell explained his decision to stand down after defecting from the Tories.
"I resigned from Parliament to face this election because I answer first, foremost and last to you, you are my boss, I will not let you down," he said.
"To my new party I offer these thoughts: humility when we win, modesty when we are proved right. If we speak with passion, let it always be tempered by compassion. We must be a party for all Britain and all Britons: first and second generation as much as every other.
Our strength must lie in our breadth. If we stay true to that there is nothing that we cannot achieve. Nothing we cannot achieve in Essex and East Anglia, in England and the whole country beyond."
Douglas Carswell has stormed back to Parliament as the new UKIP MP for Clacton increasing the majority he won as a Conservative in 2010.
He took 60% of the vote knocking the Tories back to 25%. Labour were third and the Liberal Democrats lost their deposit having been relegated into fourth place by the Greens.
Douglas Carswell has won the Clacton by-election to become the first elected Member of Parliament for UKIP. He had a majority of 12,404 which even bigger than that he achieved at the last General Election.
Mr Carswell was a Tory MP for the constituency but forced a by-election after defecting to UKIP in September.
- Douglas Carswell (UKIP) - 21,113 (59.7%)
- Andy Graham (Lib Dem) - 483 (1.4%)
- Howling Laud Hope (Loony) - 127 (0.4%)
- Charlotte Rose (Ind) - 56 (0.2%)
- Bruce Sizer (Ind) - 205 (0.6%)
- Chris Southall (Green) - 688 (1.9%)
- Giles Watling - (Con) - 8,709 (24.6%)
- Tim Young - (Lab) - 3,957 (11.2%)
The turnout was 51.2%.
Douglas Carswell is the first MP with a direct mandate for UKIP. The first UKIP MP was Bob Spink, the MP for Castle Point in south Essex. He defected from the Conservatives in 2008 but didn't force a by-election and subsequently wasn't re-elected.