Bird & Bird has lost another partner in Asia as employment partner Grace Chen has left the firm to join Covington & Burling, just a month after the firm lost a six-lawyer team.

Chen joins Covington's Beijing office after more than 15 years' practising in China.

Christopher Walter, chair of Covington's international employment practice, said that employment law advice has become a key concern for the firm's corporate clients in a "challenging" employment market for international companies in China.

Chen's departure comes on the back of a six-lawyer exit from Two Birds to intellectual property consultancy Awapatent last month. The departing team included IP partner Ai-Leen Lim.

Last August two Hong Kong partners also left the firm for Osborne Clarke: the head of Bird & Bird's communications, media and technology group in Hong Kong and China, Marcus Vass, and transactional group partner John Koh.

Two Birds has moved to bolster numbers in recent months, however, picking up corporate partner Wing On Chui from King & Wood Mallesons and Taylor Wessing competition counsel Zhaofeng Zhou earlier this year.

Late last year the firm also appointed DLA Piper of counsel Ying Wang as a partner in its international HR group in Shanghai.

In 2013 Two Birds reviewed opportunities for expansion in Asia, including potential cooperation arrangements in Indonesia and South Korea, eventually entering partnership agreements with South Korean firm Hwang Mok Park and Indonesian firms K&K Advocates and Nurjadin Sumono Mulyadi & Partners, in February and June last year respectively.

The firm now has a short-term target to grow its Asia practice from around 15% to 20% of firmwide revenue and lawyer headcount.