West Ham vice-chairwoman Karren Brady has warned that the UK leaving the EU would have "devastating consequences for the competitiveness of British football" and has called on clubs to publicly back an "In" vote ahead of the forthcoming referendum.
In a letter to the chairs of all professional clubs in the UK, Brady has written that "sitting on the side-lines cannot be an option in this referendum and I would urge you to speak up on the benefits for your club".
Brady, who sits on the board of campaign group "Britain Stronger in Europe", argues that without the EU's freedom of movement laws football clubs will it harder to attract the best players from the continent and be left at a disadvantage to their European rivals.
She writes: "For clubs, free movement plays a big role in transfers and players’ contracts. Players from the EU can sign for UK clubs without needing a visa or special work permit, making it quicker and easier to secure top talent from across Europe to come and play in our leagues.
"Indeed, there are nearly 200 premier league footballers alone who have benefited from this arrangement.
"Leaving the EU could have a big impact on foreign players, as independent analysis has shown that two-thirds of European stars in England would not meet automatic non-EU visa criteria and therefore might be forced to leave."