Net migration to the UK has risen to 298,000, according to the final set of figures before the election.
The numbers, for the year ending in September 2014, are now well above the level of migration when David Cameron came to power in 2010.
The Tories, who had promised to get it to below 100,000, said the figures were "disappointing" and blamed a rise in EU migration - and Lib Dem "constraints".
Labour said Mr Cameron's "grand promises" were "now in tatters".
Downing Street said the rise in immigration was driven in part by Britain's economic success relative to its neighbours in the eurozone.
'Blown off course'
Mr Cameron's official spokesman declined to comment on whether he would repeat his pledge to reduce immigration to "tens of thousands", but said the effort to reduce numbers was "going to be a challenge for the next parliament".
The prime minister vowed to get net migration down to "tens of thousands" each year "no ifs, no buts" in a speech in 2011, adding "that's a promise we made to the British people and it's a promise we are keeping