Conservative chairman Francis Maude has promised a "wide-ranging review" of the party's immigration policy.
Mr Maude said the process would be "painstaking"
He told BBC Radio 4's World at One programme it was important to show Tories did not have an "antagonism" and that they were "decent people".
A party spokeswoman said a general election pledge to introduce an annual asylum seeker quota was being reviewed.
Mr Maude said immigration had been "fantastically good" for the UK but had to be "controlled".
He added: "We are going to go through a very painstaking, serious programme of policy reform and renewal to work out what are the right answers - hard-edged, Conservative answers - for 21st-Century Britain."
The party is calling for a scheme that requires some eastern Europeans to pay £70 to work in the UK to be scrapped.
This would allow more accurate figures on how many migrants are employed, it says.
The European Union worker registration scheme applies to people coming to Britain from the eastern European countries which acceded to the EU in May 2004.
These were the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia and Slovenia.
It requires workers to pay for a form and submit this, along with their passports, to the Home Office.
The Tories say the cost causes "mass evasion" by those looking for low-paid jobs.
The party also cites research suggesting that between 90,000 and 150,000 workers from the new member states were working in agriculture and fresh produce in one year, around three times the official figure.
But a Labour Party spokeswoman said the scheme had been introduced to reassure the public.
She admitted some people were coming in on the black market and that no monitoring system was perfect.
But she added: "If you are removing it, you need to think about what you would put in its place - we are proposing e-borders and ID cards."
Self-employed workers do not have to register under the scheme.
Once workers have been in the UK for a year, they are granted full rights of free movement, do not have to register with the scheme and can apply for a residence permit.