David Cameron today appealed for the public to "shop" illegal immigrants as he pledged to reclaim Britain's borders.
The Prime Minister said he wanted the whole country to help the Government tackle the issue by reporting suspicious individuals.
He also insisted the citizenship test for legal incomers would be rewritten to include questions on British history and signalled a fresh crackdown on forced and bogus marriages.
The moves were revealed as Mr Cameron delivered a keynote speech setting out plans to control immigration.
In future, individuals applying to come to the UK for family reasons will have to show that they can speak English and have the financial means to support themselves as well as genuine family links in Britain.
Family migration made up almost a fifth of non-European Union (EU) immigration last year, with 50,000 visas issued, he told an audience at the Institute for Government in central London.
But a survey suggested that more than 70% of UK-based family sponsors had an income of less than £20,000 after tax, creating "an obvious risk" that they may become dependent on welfare.
Mr Cameron said the Migration Advisory Committee (MAC) would consider whether the minimum level of financial support should be higher and whether a "bond" from migrants could be demanded in some cases.
There will be closer checks on claimed relationships between spouses to weed out sham marriages for immigration reasons, including cases where couples divorce immediately after obtaining permission to stay and then make fresh applications relating to different partners.
"We will make migrants wait longer, to show they really are in a genuine relationship before they can get settlement," Mr Cameron said.
"We'll also impose stricter and clearer tests on the genuineness of a relationship, including the ability to speak the same language and to know each other's circumstances.
"We will also end the ridiculous situation where a registrar who knows a marriage is a sham still has to perform the ceremony."
He added that he wanted the coalition to "go further and be even tougher" on immigration.
"For our part in government, we are creating a new National Crime Agency with a dedicated border policing command which will have responsibility for safeguarding the security of our border," he said.
"But I want everyone in the country to help, including by reporting suspected illegal immigrants to our Border Agency through the Crimestoppers phone line or through the Border Agency website.
"Together we will reclaim our borders and send illegal immigrants home."
He said he would rewrite the exam for migrants wishing to take on UK citizenship to ensure that British history and culture - rather than EU institutions and the workings of the benefit system - are at the heart of the tests.
Mr Cameron denounced Labour's points-based system, which was intended to ensure that economic migration was limited to those workers needed by the UK economy, as a "complete failure" which was "a magnet for fraudsters" and allowed the number of incomers to go "through the roof".
Initial indications suggest that the Government's actions since coming into office in May last year have started to reverse a trend which saw net migration rise to 239,000 last year, he said.
A new annual ceiling of 20,700 non-EU economic migrants had been undersubscribed every month and the Government was asking the MAC to consider reducing it further.
He restated his goal of getting net immigration down to the tens of thousands.
But he said he was determined to give "the red-carpet treatment" to entrepreneurs, investors and scientists from overseas who want to come to Britain to create businesses and jobs.
He said he recognised there was "discomfort and tension" in some communities over the arrival of large numbers of migrants and insisted that the Government was not "powerless" to deal with it.
He promised to deliver "fairness for people already living here, working here, contributing here, who worry about finding work, getting a good school for their children and affording a good house".
"For too long, they have been overlooked in this debate. And it's time to do right by them," Mr Cameron said.
The PM also signalled that forcing someone to marry against their will could become a criminal offence.
He announced he was making it illegal to breach an order issued by the courts to prevent a forced marriage and has asked Home Secretary Theresa May to consult on whether the practice should be criminalised in England, Wales and Northern Ireland.
The cross-party Commons Home Affairs Committee backed such a move earlier this year but its recommendation was rejected by the Home Office in July for fear that it would discourage victims from coming forward.
Committee chairman Keith Vaz welcomed the announcement on forced marriage.
But he warned that the idea of demanding a financial "bond" from would-be immigrants should be treated with "extreme caution".
"This is the third time this proposal has been put on the table since 2000," Mr Vaz said.
"It will antagonise settled communities and enrage our allies such as India. It was shelved before because it was unworkable. A more effective method must be found in order for immigrants to pay for public services."
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