MILAN (Reuters) - Vivendi already had access to a business plan for Mediaset's pay-TV unit before agreeing to buy it, the Italian broadcaster said on Friday as the two companies kept trading punches over a u-turn by the French media firm on the deal.

Mediaset accused Vivendi of releasing market-sensitive data after the French group issued a statement saying a business plan for the division called Premium was based on "unrealistic assumptions".

"Vivendi will have to face civil and criminal action also over the damages (caused)," Mediaset said in a statement.

On Thursday the company owned by former prime minister Silvio Berlusconi said that it would seek legal action against Vivendi over its abrupt change of heart regarding a share-swap deal that would have given the French the full control of Premium.

(Reporting by Giulia Segreti, editing by Agnieszka Flak)