PARIS (Reuters) - France's Natixis said on Monday it had agreed to buy stakes in three independent boutique advisory firms - Fenchurch Advisory Partners LLP, Vermilion Partners and Clipperton - as it seeks to diversify its investment banking activities.

The bank did not disclose the value of the deals, but estimated that the three investments would reduce Natixis' common equity tier one ratio by around 8 basis points.

Natixis plans to buy a 51 percent stake in Fenchurch, which is focussed on corporate finance advisory to financial services companies in Britain. The firm, which has advised on over 200 completed transactions worth more than 150 billion pounds ($208 billion), will continue to be managed by current partners, Natixis said.

The French bank has also agreed to buy a majority stake in Vermilion Partners, which focuses on cross-border mergers and acquisitions (M&A) involving China. Natixis is also buying a minority stake in French M&A boutique specialised in high-growth technology.

"The acquisition of key expertise in financial services, China and European Tech is complementary to our existing franchise," Marc Vincent, global head of corporate and investment banking at Natixis said in a statement.

In February Natixis reported an unexpected rise in quarterly net profit as a one-off gain linked to the U.S. tax reform and stronger revenue growth in asset management helped offset a widespread trading slowdown.

($1 = 0.7197 pounds)

(Reporting by Matthieu Protard and Maya Nikolaeva, editing by Dasha Afanasieva)