Home Secretary Theresa May said coalition rows were holding back efforts to cut immigration as she indicated further curbs were under discussion.
Deporting EU nationals who are not working and halving the length of time others can claim benefits are among proposals on the table, she said.
She spoke out about "heated" rows with Liberal Democrat colleagues as the mainstream parties sought to beef up their stance to counter the growing electoral threat from Ukip.
She conceded that David Cameron's aim of reducing net migration to the tens of thousands "has become more difficult" after official figures showed the number was still going up.
"We still have that aim of the tens of thousands. But of course it has become more difficult and net migration is too high," she told BBC1's Andrew Marr Show.
"That's why I want to continue working to bring it down.
"In those areas we can control - that is, immigration from outside the European Union - everything we have done as a Government has been having an impact."
She confirmed a report in the Sunday Telegraph that deporting people who exercised the right to come to the UK to work but could not find a job was among measures being considered.
Work and Pensions Secretary Iain Duncan Smith told the Sunday Times he wanted to introduce new laws this year to restrict benefit claims to three months.
The length of time EU migrants must wait before claiming has already been extended from three months to six, with the Tories and Labour indicating that period could be made longer still.
"You'll have to wait three months and you'll only be able to claim for three months. Then it's bye-bye. That's quite a significant tightening up," Mr Duncan Smith said.
Mrs May told the BBC: "We have been looking at various measures and we will continue to look at measures."
Asked about Mr Duncan Smith's plans, she said: "We will look at that timing.
"We haven't yet got agreement across the coalition to do that. But these are the sorts of measures we keep looking at because in immigration you can never stand still."
She went on: "It is no surprise to anybody that there have been some long-standing, possibly heated at times, discussions among the coalition on some of these issues of immigration."
Official figures, released on the day voters went to the polls in local and European elections after a campaign dominated by immigration, showed another significant jump in immigration to the UK from within the European Union.
The Office for National Statistics (ONS) said net migration increased to 212,000 in the year to December, from 177,000 the previous year.
This was driven by a "statistically significant" increase in EU citizens immigrating to Britain, which the Government has little power to control, from 158,000 to 201,000 year-on-year.
Asked whether the "tens of thousands" had not been a "pledge" by the Prime Minister, Mrs May said: "It has always been a target for us to drive towards that."
Shadow immigration minister David Hanson said the proposals reportedly under discussion were "m ore headline chasing but less effective action from the Tories on immigration".
He added: "David Cameron and Theresa May's last immigration Bill was a complete car crash with Government ministers abstaining on their own policies.
"Having lost so many votes and seats on Thursday while his net migration target is failing badly, David Cameron is clearly rushing for more headlines before he has a policy in place.
"We've been calling for over two years for the Government to act to stop employers exploiting immigration to undercut wages and jobs.
"Yet the Tories and Liberal Democrats voted against our proposals. These sketchy new suggestions don't go far enough to address the impact on wages and jobs.
"We need stronger border controls, action to make serious exploitation a criminal offence, tougher fines and enforcement, and also to remove students from the net migration target.
"We must move to a credible immigration working for everyone but all this Government is interested in is the next headline."
Shadow home secretary Yvette Cooper said: "David Cameron and Theresa May promised 'no ifs, no buts' they would cut net migration to the tens of thousands by the end of this Parliament.
"Yet four years into the Parliament the figures have been going up not down, and it is currently more than double their target.
"For the Home Secretary to keep making big pledges and failing to meet them undermines trust in the whole immigration system.
"Having lost so many votes and seats while their net migration target is failing badly, the Tories seem to be rushing for more headlines before they have policies worked out.
"Instead they should accept the practical policies we have put forward over the last two years to strengthen border control, tackle the impact of immigration on wages and jobs, reform EU controls, and replace the net migration target with a smarter system.
"Immigration is important for Britain and that's why it needs to be properly controlled and managed. Public concern about immigration is considerable. That's why we need sensible, fair policies, not just rhetoric, headlines and more failed targets."