This is the problem as I see it:
Migrant worker is probably a single male who lives in a shared house with a load of others. He works for the minimum wage because he CAN. The Brit worker with mortgage and family can't so he's better off on benefits.
What this means is the migrant worker on low pay pays little if any tax. The Brit on benefits draws money out of the national pot. The migrant worker doesn't spend his money in Comet and Waitrose - he sends it out of the country to benefit his home country. The Brit worker on benefits has no money to spend in the shops - so the shops suffer and reduce branches and staff numbers. The redundant staff then claim benefits.
Because the government is then paying out on benefits yet receiving no income tax from the migrant - the books don't balance and so the Government has to borrow more money - and the burgeoning deficit continues to rise.
To get the deficit down the Government needs to reduce benefit payments and they need to get more tax in. Then (and only then) can they reduce the dangerously high national debt.
So what we need is to employ British people who spend their pay in the UK. They should be paid a decent wage so in turn they pay a decent amount in tax and the deficit can be controlled.
Forcing wages too low is the economics of madness.
There'll be tears before bedtime.