LONDON UBS announced an overhaul of its investment banking division on Monday, including naming the unit's M&A chiefs, marking a key step in integrating Credit Suisse.

Sergio Ermotti is seizing on the opportunity presented by the rescue takeover of Credit Suisse in March to reorganize UBS' investment bank to better compete against Wall Street firms.

UBS is hiring top bankers from competitors as well as promoting staff from within its ranks and Credit Suisse as part of the shake-up, which will also lead to hundreds leaving.

As a result of the investment bank overhaul, Credit Suisse's David Kostel will become Global Co-Head of Coverage while Tom Churton, also from Credit Suisse, was named Global Chief of Staff, a memo to staff seen by Reuters showed.

Christian Lesueur, who was Global Head of TMT Investment Banking at UBS, has been promoted to Global Co-Head of Coverage and will continue to oversee technology, media and telecoms, which will now be split into two groups.

Nestor Paz-Galindo and Marc-Anthony Hourihan will be Global-Co-Heads of M&A in the merged organization.

UBS said Michael Santini, former Executive Chair of Global Banking, is among executives who will leave as a result of the changes, some of which were reported on by Reuters on Friday.

UBS could axe around 30% of its combined workforce, which has expanded to 120,000 after the state-brokered rescue, Reuters reported in June, with Credit Suisse's investment bank, back office, and its Swiss retail bank likely taking the biggest hit.

Hundreds of Credit Suisse bankers have already left to other institutions and UBS has been laying off employees from Credit Suisse's investment bank around the globe.

Around 80% of Hong Kong-based investment banking staff at Credit Suisse will be laid off and the cuts will start from this week, Reuters also reported on Monday, citing two people with knowledge of the matter.

Hong Kong makes up Credit Suisse's biggest share of investment bankers in Asia.

Other UBS changes announced on Monday include Marc Warm, who will join David Slade as Global Co-Head of Leveraged and Debt Capital Markets, while Scott Lindsay and Robin Rankin will both be Global M&A Chairman.

(Reporting by Andres Gonzalez and Oliver Hirt; Editing by Elisa Martinuzzi and Alexander Smith)