Theresa May told the BBC the current quotas on immigrants from Bulgaria and Romania will expire as scheduled next year, meaning a possible influx of people from those two nations pouring in under the European Union's "freedom of movement" rules.
"There are no further transitional controls that we can put on -- the transitional controls end in December 2013," May said.
Quotas remain in place on Bulgaria and Romania since those two nations joined the EU in 2007. The Sunday Telegraph said analysts noted an uptick in new arrivals from Poland and other Eastern European nations when their transitional quotas expired in 2004.
May said the situation illustrated the need for the British government to take a new look at the nation's social benefits and whether they were fueling the growth of immigration.
"I will be looking at what we call the pull factors, what is it that attracts people sometimes to come over here to the United Kingdom," May said.