It is thought Clifford Chance made the first approach in a bid to boost its corporate finance practice. It is believed the firm was due to vote on the proposed marriage two weeks ago. But a merger is now not going ahead.
Clifford Chance's managing partner Tony Williams would say only that 'the firm is not in merger talks'.
Andrew Soundy, Ashursts senior partner, said: 'We are a firm which is perceived as attractive. A lot of people talk to us from time to time. I'm not prepared to comment in regard to any specifics.
'We always listen when people make contact with us and are courteous with them.'
Clifford Chance is one of the world's leading banking and finance practices but it is weak in corporate finance.
Ashursts, on the other hand, has never had a strong banking practice and is trying to build one. But it is widely respected for its strong corporate client base.
It also has a relatively weak international presence, with only small offices in Paris, Brussels, Singapore, Frankfurt, Tokyo and New Dehli, making it difficult to service multi-national clients in transactions outside the UK.
A merger with Clifford Chance would have given Ashursts the international offices it needs. However, the move would have been an effective takeover by Clifford Chance and many Ashursts partners are proud of their long independence.
Clifford Chance was formed by merger 10 years ago, while Ashursts last year celebrated 175 years of organic growth without a name change.