Nick Clegg is to promise a clampdown on sham marriages to tackle an "industry" which he said was resulting in a reported 2,000 fake weddings a year to get round immigration rules.
The Deputy Prime Minister will say that the Government is also to spend more than £1 million on tougher inspections to target exploitative employers using migrants as cheap labour on less than the minimum wage, with a particular focus on care homes, recruitment agencies and hotels.
Provisions in the coalition Government's Immigration Act, passed earlier this year, extend the notice period for weddings and civil partnerships from 15 to 28 days in order to allow more time for investigation to check that they are genuine.
Ministers have made clear they expect registrars to report suspicions to the Home Office, which has new powers to delay nuptials for a further 70 days while inquiries take place.
In a speech later this week, Liberal Democrat leader Mr Clegg is expected to say: "We are clamping down on sham marriages.
"It's an industry - and a growing one, with around 2,000 reported every year. When people want to remain in the UK, they'll do everything they can to stay.
"As we close more loopholes, more and more people who don't have permission to live in Britain are paying to marry someone who does."
Mr Clegg will warn that criminal gangs are using vulnerable women from eastern Europe - who are allowed to enter the UK as European Union citizens - as "anchor brides", charging illegal immigrants from outside Europe thousands of pounds to marry them.
The Deputy Prime Minister will say that the Government is enlisting Britain's registrars in the fight to make it harder to stage sham weddings.
"It is an insult to their profession and the institution of marriage when they have to conduct a ceremony and the groom doesn't even know his future wife's maiden name," he will say.
"There are many registrars who, up until now, have been unsure of what is required from them, so we have written into the Immigration Act that we expect registrars to tell the Home Office of any suspicion they have that a couple is bogus or an individual is here illegally.
"We've also issued advice directly to all registrars so they know exactly what to do.
"On top of that, from next year we are also going to extend the notice period for all couples seeking to marry or enter into a civil partnership from 15 to 28 days, and when someone rings the alarm we'll be able to pause proceedings for 70 days while the Home Office investigates.
"Currently a marriage application can be refused if we can prove it's fake - but that can be extremely difficult when the Home Office has such little time to react. This way we build in a break on sham marriages speeding through registry offices."
On breaches of minimum wage legislation, Mr Clegg will say: "The Government is upping the number of inspectors tasked specifically with identifying businesses using migrants as cheap labour - paying below the minimum wage.
"We're investing over a million pounds in a beefed-up, bespoke team.
"Rather than just respond to tip-offs, they will pro-actively go after the worst offending employers, including those who run care homes, recruitment agencies and top-class hotels."
But Labour home affairs spokeswoman Baroness Smith said: "Unfortunately for Nick Clegg, the real gaps in our immigration system have opened up under his Government.
"There has been an explosion in sham marriages being used to get around the rules and there have been only three prosecutions for breaches of the national minimum wage since 2010.
"Despite being warned repeatedly about these gaps in the system, the Home Office and the Lib Dems have ignored us.
"Indeed, when they had the chance to vote for measures to tackle sham marriages and minimum wage exploitation that we brought forward as part of the immigration bill passage, they voted against them.
"You can't trust a word Nick Clegg and the Lib Dems say."