Former Environment Secretary Owen Paterson has dismissed reports that he is considering joining Ukip as "absolutely laughable".
Mr Paterson, who is seen as a strong eurosceptic voice in the Conservative Party, hit out at the "unhelpful" defections of former Tory MPs Douglas Carswell and Mark Reckless.
He also hit out at Mr Reckless' suggestion that the UK could curb immigration by leaving the EU.
"When you see Mark Reckless saying getting out of the EU would solve it, I'm afraid his facts are wrong."
Mr Paterson pointed out that Switzerland and Norway have higher immigrant populations than the UK, despite not being EU members.
Conservative Party Chairman Grant Shapps told the party conference defecting Mark Reckless has "abused" their trust.
"Today your trust has been abused, you have been cheated, but worse, the people of Rochester and have been cast aside," Shapps said.
Nigel Farage suggested there might be Labour Party members who could defect to Ukip.
"There are people sitting on the Labour backbenches [who are] dismayed, absolutely dismayed, that Ed Miliband doesn't appear to want to do anything to help working people," Farage said.
Conservative defector Mark Reckless has rejected charges he acted in bad faith in leaving the party for Ukip.
The MP for Rochester and Strood insisted he was "trying to do the right thing by his constituents" and accused David Cameron of breaking his election promises.
"I made a lot of promises to my constituents and I want to keep those promises on immigration, on the deficit, on political reform. The Prime Minister isn't keeping those promises, I want to do so and that's why I'm moving to Ukip," he told BBC's Sunday Politics.
"We made all these promises in 2010 as Conservatives and they have been broken."
Prime Minister David Cameron has described Mark Reckless' defection to Ukip as "frustrating" and "rather senseless".
Asked on the BBC's Andrew Marr Show if he was aware Reckless was leaving the Conservatives, Cameron said, "Not specifically but ... he very rarely votes for the Government and has made his views known."
"Look, these things are frustrating and frankly they are counterproductive and rather senseless," he continued.
"If you want to have a European referendum, if you want to have immigration control, if you want to get the deficit down, if you want to build a stronger Britain that we can be proud of, there is only one option and that is to have a Conservative Government after the next election."
Ukip leader Nigel Farage has said it "wouldn't surprise me" if more MPs defected to his party following Mark Reckless' decision to leave the Conservatives.
Farage told the BBC's Andrew Marr Show, "There is a widespread feeling that the political leaderships of Labour, Lib Dem and Conservative are becoming so hopelessly out of touch with opinions in MPs' constituencies that it wouldn't surprise me if we saw more defections."
Ukip leader Nigel Farage has shot down proposals for the party to levy a "luxury goods tax" on items such as designer shoes and handbags.
Economic spokesman Patrick O'Flynn put forward the idea of a 25% VAT rate for top-end goods at the Ukip annual party conference in Doncaster.
But Mr Farage has moved to kill off the idea, saying it was no more than a "discussion point" that "isn't going to happen".
"I'm pretty certain that while I'm leader that will not be in our manifesto," he said in an interview with BBC1's The Andrew Marr Show to be broadcast today.
Colourful and outspoken Ukip member Winston McKenzie has lauded Nigel Farage as 'the world's greatest leader'.
Speaking as Farage introduced new member Mark Reckless to some of the party faithful, McKenzie could not hide his excitement and lavished praise on Mr Farage.
Conservative MP Mark Reckless has turned his back on the party and pledged his future to Ukip.
ITV News Political Correspondent Romily Weeks reports on the second Tory MP to leave the party in less than a month.
The chairman of the Rochester and Strood Conservatives said he was "astonished and disgusted" by Mark Reckless' decision to defect to Ukip.
I am astonished and disgusted by Mark Reckless' decision - only 48 hours ago he proclaimed his support for the Conservatives and their plans for a referendum on Europe and he gave me assurances he wouldn’t defect.
He has misled the hardworking people of Rochester and Strood who voted for him. It is only the Conservatives who can deliver a referendum on Europe with a vote for UKIP being a vote for Ed Miliband.