Labour has ignited a row with supermarket giant Tesco (Other OTC: TSCDF - news) by planning to attack the chain for employing foreign workers.

Shadow immigration minister Chris Bryant is due to condemn Tesco and other leading companies for being "unscrupulous" and pursuing cheap labour from Eastern Europe.

In a speech on Monday, he is expected to claim Tesco moved its distribution centre to Kent where a "large percentage" of the staff are from the eastern bloc.

The firm has already hit back, denying having a distribution centre in the county and insisting it does not actively seek to recruit abroad.

A spokesman said: "It is wrong to accuse Tesco of this. We work incredibly hard to recruit from the local area and have just recruited 350 local people to work in our Dagenham site."

The company is also understood to be writing to Labour to complain about the "unfair" slight.

Mr Bryant's speech appears to be the Opposition's latest attempt to wrestle back the initiative on immigration, which is a top concern for British voters.

The party is also battling to get on the front foot after a quiet summer which has seen their poll lead slip and Ed Miliband face internal criticism for failing to set the agenda.

Mr Bryant will admit immigration can have a negative effect on labour markets, according to extracts from the draft speech reported in The Sunday Telegraph.

"The biggest complaint I have heard, from migrants and settled communities alike, is about the negative effects migration can have on the UK labour market. And I agree," he is due to say.

"It is unfair that unscrupulous employers whose only interest seems to be finding labour as cheaply as possible will recruit workers in large numbers in low-wage countries in the EU, bring them to the UK, charge the costs of their travel and their substandard accommodation against their wages and still not even meet the national minimum wage.

"That is unfair. It exploits migrant workers and it makes it impossible for settled workers with mortgages and a family to support at British prices to compete."

He will claim Tesco had recently decided to move its distribution centre in Kent but slashed pay for existing staff, penalising Britons.

"The new centre is larger and employs more people, but the staff at the original site, most of them British, were told that they could only move to the new centre if they took a cut in pay," he will say.

"The result? A large percentage of the staff at the new centre are from [the] Eastern bloc."

As well as highlighting the recruitment of hundreds of local staff, Tesco made clear that the distribution centre is in the east London borough of Barking and Dagenham and was formerly in Essex, not Kent.

Mr Bryant's address is also set to target high street chain Next (Other OTC: NXGPF - news) , who he accused of printing leaflets in Polish to attract workers from the country.

Extracts from his speech say: "Look at Next Plc (LSE: NXT.L - news) , who last year brought 500 Polish workers to work in their South Elmsall warehouse for their summer sale and another 300 this summer.

"They were recruited in Poland and charged £50 to find them accommodation. The advantage to Next? They get to avoid Agency Workers Regulations, which apply after a candidate has been employed for over 12 weeks, so Polish temps end up considerably cheaper than the local workforce, which includes many former Next employees."

The MP's speech will make clear that neither firm has broken the law.

After the extracts emerged, Next admitted using Polish agency workers to help fill slots during the summer sale but vehemently denied it was done to cut costs.

A spokesman said: "We are deeply disappointed Mr Bryant did not bother to check his facts with the company before releasing his speech.

"In fact agency workers from Poland cost us exactly the same as local agency workers, and our existing employees.

"The only reason we seek the help of people from Poland is that we simply can't recruit enough local people to satisfy these spikes in demand for temporary work."

The firm also made clear the nationality of workers had no effect on their rights under Agency Workers Regulations.

"We very much hope that Mr Bryant, being apprised of the facts, will reconsider his claims when he comes to make his speech," it said.

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