Hundreds of skilled but unemployed construction workers gathered outside the EON power station on the Isle of Grain on Wednesday morning to protest over the use of foreign labour in the UK.

A gas-fired plant is being built at the site by lead contractors Alstom but the trade union Unite, which has organised the demonstration, claims the company is using two sub-contractors who are refusing to consider local labour.

But the company insists its recruitment policy is fair.

A statement released by Unite says: "At the Isle of Grain, two sub-contractors have refused to consider applications for work from UK-based labour. Unite estimates that the two sub-contractors will require 450 workers over the lifetime of the project. Alstom has been contracted by E.ON to build the power station.

"Unite is calling on the government to insist that companies applying for contracts on public infrastructure projects, sign up to Corporate Social Responsibility agreements which commit to fair access for UK Labour."

Alstom says it has about 15 sub-contractors working at Grain, the overwhelming majority of which are British, with only two being non-UK companies.

A spokesman said: "We always give British firms and workers an equal chance to bid for work on the project. We do not and will not discriminate."

Derek Simpson, Unite's joint general secretary, said: “Unemployed construction workers are asking for fairness not favours.

"UK-based labour must be given a fair chance to get a cut of the action to build a new generation of UK power stations.

"As the protest takes place on the Isle of Grain the Unite union will hand in a petition to Downing Street calling for UK workers to be given fair access to work on British construction jobs.

Union leader Derek Simpson will lead the delegation after thousands of construction and engineering workers signed the petition, many of whom are currently out of work.

The petition also calls for migrant construction workers to receive fair pay when working on projects in the UK.

Medway Police say they will be ready to deal with any problems.

Chief Insp Iain Mackenzie said: We have been made aware that a peaceful protest is planned to take place tomorrow at the Alstom site in Grain.

"We have been in regular contact with both Alstom and Uniten) to ensure that the safety of local residents and the protestors is paramount, should the protest go ahead.

It is believed that there will be between 50 and 200 protestors present at the site.

Chief Insp Mackenzie said:" If anything is brought to our attention we will act swiftly and aim to keep disruption to local residents to a minimum.

Meanwhile, Alstom has applied to Medway Council for planning permission to moor an accommodation barge at Damhead Creek from January,2009,to November,2010.

The barge is expected to house up to 200 specialist workers employed at the Grain Combined Heat Project for E.ON at its Isle of Grain site.

But Alstom says the application is only a contingency plan.

The spokesman added: "It is common practice right across the construction industry, specifically at remote sites, to arrange temporary accommodation for workers, both British and from further afield.

"This is common knowledge and is openly available information which we have shared with the unions, as is best practice."