Cleary Gottlieb Steen & Hamilton and Italian boutique Pavesi Getti have bagged the lead roles on a E9bn (£6.1bn) merger that will create Italy's third-largest energy company and biggest local utility.

The merger between AEM and locally-listed utility ASM was announced on 1 June.

Cleary Gottlieb is representing AEM with Milan-based corporate heavyweight Roberto Casati leading a team alongside corporate partner Roberto Bonsignore.

The US-based firm has been a long-term adviser to the company. Other big-ticket mandates the firm has advised on include AEM's E8bn (£5.4bn) joint acquisition with state-owned French utility Electricite de France of a controlling stake in Italian energy company Edison in August 2005.

Pavesi name partner Gregorio Getti headed the advisory team for ASM.

Slaughter and May ally Bonelli Erede Pappalardo also secured a major role, advising the City of Milan, which has a 42% stake in AEM. Milan-based corporate partner Mario Roli took the lead role.

The tie-up is the latest in a slew of deals in the buoyant Italian M&A market.

Last month, local independents Chiomenti and Grimaldi won lead roles on the latest deal in the fast-consolidating Italian banking sector – the proposed merger between UniCredit and Capitalia, which would create a banking giant worth around E100bn (£68bn).

Chiomenti is advising Capitalia, while Grimaldi corporate partner Roberto Capelli is acting on behalf of Unicredit.

Bonsignore told Legal Week: "There has been a lot of consolidation in the Italian energy sector, but there are still sizable companies looking to merge – there will still be a lot of activity going forward."