Express Newspapers chairman Richard Desmond has reportedly pledged a £300,000 donation to UKIP.
Desmond is believed to have discussed the gift at a meeting with UKIP leader Nigel Farage earlier this month.
Sky News said it was not clear whether the money had yet been handed over.
Express Newspapers publishes the Daily Express, Sunday Express, Daily Star and Daily Star Sunday.
A Ukip spokesman said: "We do not discuss donations.
"If we receive them we report them to the Electoral Commission in accordance with legislation."