Asda parent company Wal-Mart has been named as the biggest company in the US for the second consecutive year.

The retailer giant has extended its lead at the top of the Fortune 500 list, the ranking of corporate American by revenue.

Wal-Mart has sought endless expansion, with its bid for UK supermarket chain Safeway just one way of helping to consolidate its presence in this country.

In the US, Wal-Mart – founded in 1962 - is the biggest American-owned employer with 1.3 million staff worldwide.