British steel workers will plead with ministers this week to push ahead with plans to expand Heathrow, claiming a new runway will keep steel jobs.

An estimated 370,000 tons of steel will be needed to complete the expansion which will include new terminals, securing at least 700 jobs for the next 10 years.

Union leaders, backed by MPs and business chiefs, will write to Business Secretary Greg Clarke calling on him to back plans for the third runway.

The project would require a 10th of Britain's total steel output for 2015 making the contract highly sought-after.

Heathrow has announced it plans to give British steel companies a fair opportunity in vying for the lucrative contract, rallying plants in Scunthorpe, Port Talbot and Teesside.

Labour MP Anna Turley was in support of the push. Speaking to the Sun on Sunday she said: "It will kick-start communities under threat of job cuts."

Fresh controversy emerged last week surrounding the third runway when a leaked document revealed Theresa May's plans to give ministers a free vote on airport expansion.

Prime Minister Theresa May is allegedly considering waiving Cabinet "collective responsibility" allowing Boris Johnson and Justine Greening, who are both firmly against the expansion, to openly oppose the move.

Senior Tory MP Grant Shapps speaking to Theresa May said any free vote would be an "absolute dereliction of duty".

He also condemned a free vote on a matter that involves such "an enormous decision for Britain's future".

The Cabinet is considering whether to proceed with a third runway at Heathrow or approve a rival development at Gatwick instead ahead of a vote in the autumn.

Tata Steel Britain
Steel workers support plans for Heathrow expansion Oli Scarff/AFP