West Ham say Sporting Lisbon's claims over the English club's attempts to sign midfielder William Carvalho are "without foundation".
The Hammers' proposed £23million deal for the Portugal international fell through before the transfer window closed on August 31.
But Sporting claim the Premier League club never submitted an official bid for Carvalho, which led West Ham in turn to say it would sue the Lisbon-based side.
Emails obtained by Sky Sports News appear to show there was direct communication about the player between the two clubs, with details published of an offer of €25million to be paid in three instalments across 24 months.