Prime Minister David Cameron has insisted that his promise to get immigration below 100,000 a year is still "achievable", despite predictions that figures due tomorrow will show 30,000 have come from Romania and Bulgaria alone since the start of the year.

Commons Home Affairs Committee chairman Keith Vaz cited the forecast figure as he pressed the PM to admit that - with net migration soaring to 212,000 last year - he was "not going to meet that target" by the time of the general election in May 2015.

But Mr Cameron insisted: "The target remains. I think it is absolutely achievable". Appearing before the House of Commons Liaison Committee, he declined to discuss the figures for Romanians and Bulgarians before their publication, but said that his administration had brought net migration down by one-fifth since coming to office.

The PM also resisted pressure to end the inclusion of foreign students in the net migration statistics, which has helped hold the figure down but has been blamed by critics for cutting the overseas income of UK colleges.

Mr Cameron insisted that the fall in overall numbers of foreign students was driven by action to shut down hundreds of "bogus" colleges, and cited statistics showing that numbers of genuine overseas students at British universities had risen from 142,000 to 162,000 since 2010.

He said that the UK was making an "incredible offer" to would-be students from overseas, by saying that there would be no limit on the numbers who can study at a British university, provided they have an English-language qualification and an offer of a place. He called on universities to "get out around the world and market this".

Mr Cameron said: "What we have managed to achieve is exactly what we wanted to achieve, which is the numbers of university students going up, the number of bogus colleges eradicated and the numbers overall coming down.

"I actually believe we have completely got the right policy."

Mr Cameron insisted that controversial powers to strip terror suspects of their British citizenship were necessary as he was told that the move put the UK in a group with countries including Zimbabwe and Russia.

He said there was a "very serious problem" posed by people travelling from the UK to Syria who risked being radicalised.

Hywel Francis, chairman of the Joint Committee on Human Rights, said: "We will be in strange territory where we would be having powers with a small group of countries like Zimbabwe and Burma and Russia and Serbia which exercise such powers."

He asked if the threat of being stripped of British citizenship will be used to threaten "every naturalised citizen who goes to Syria".

Mr Cameron said: "To me, the first priority of a prime minister is to help keep the country safe, particularly from terrorists, terrorism and people who threaten our way of life.

"The fact is, deeply regrettably, there are people in our country - who might be British citizens or dual nationals - who mean to visit on us extreme harm. If taking away their citizenship and excluding them from returning to our country can help keep us safe, then we should absolutely do that and that's why this power is important."

The proposals were watered down during their passage through Parliament and the Home Secretary would not be able to use the power without ''reasonable grounds'' to believe an individual could regain citizenship elsewhere. There will also be a review after 12 months.

But Mr Cameron added: "Hundreds of our British citizens or dual nationals have travelled to Syria or attempted to travel to Syria and we need to use everything in our power to stop them from going, to stop them from being radicalised, to deal with them if they are and keep our country safe.

"This is a very, very serious problem."