UniCredit's bid risks scuppering the government's plans to form a third strong banking player alongside Intesa Sanpaolo and UniCredit through a merger of BPM with state-owned Tuscan lender Monte dei Paschi di Siena (MPS), both of which have ties with Italy's biggest fund manager, Anima Holding.

The 10 billion-euro ($10.52 billion) bid presented by UniCredit on Monday was not previously agreed and was delivered on "unusual" terms, the Banco BPM board of directors said in a CNBC-translated statement. It also failed to reflect Banco BPM's profitability and potential for further value creation, the board added.

UniCredit SpA has hired Deloitte LLP to advise Italy’s second-biggest bank on its takeover bid for Banco BPM SpA, people familiar with the matter said.

UniCredit's bid for BPM also throws a spanner in the works for Italy's government, which had advanced plans for a merger of BPM with rival Monte dei Paschi di Siena which it saw as strengthening its banking sector without harming competition.

UniCredit SpA informed top officials in the Italian government and Banco BPM SpA Chairman about its intention to make a takeover bid for its smaller rival before announcing the move on Monday, people with knowledge of the matter said.

The Italian government is ready to use its special vetting powers if UniCredit's takeover bid for smaller rival Banco BPM goes against the national interest, the prime minister said on Monday. "This is a market operation