Allen & Overy (A&O) has once again come out on top of the latest global project finance league tables, leading its rivals by value and volume for the first half of 2007.

Research by Infrastructure Journal shows A&O on top after advising on 35 deals worth a combined $27.4bn (£13.4bn). Clifford Chance (CC) is in second place by value, with 24 deals worth $23.2bn (£11.3bn), while New York law firm Shearman & Sterling completes the top three by value after acting on deals worth $15.3bn (£7.5bn).

Notable advisory roles for A&O include acting on Saudi's $1.88bn (£917m) Shuquaiq water and power project, the $2.7bn (£1.32bn) Nanhai Petrochemicals project in China and Qatar's $2.4bn (£1.17bn) Messaieed power project.

A&O projects partner Calvin Walker commented: "The push seems to be in the Middle East and China, where we have been active for some time and [Shanghai chief and infrastructure specialist] Simon Black is making good inroads."

He added: "We are opening a new office in Saudi and this has been very well timed with Abu Dhabi and Saudi opening at the same time in addition to the growth of non-energy projects in that region."

The tables for the end of 2006 had CC placed first by value, with magic circle rival Linklaters in second and A&O placed third. However, A&O's much-vaunted projects team topped the year-end tables by volume, advising on 44 deals against 34 for CC.

Linklaters, meanwhile, has dropped into fourth position by value and third by volume for the first half of 2007, with 21 deals worth $13.1bn (£6.4bn).

Norton Rose improved its ranking to move from 10th to sixth in the overall global adviser table, with 19 deals worth $10.2bn (£5bn).

However, City rival Herbert Smith – which ranked 8th in the 2006 year-end tables – fell to 58th position in the latest figures, advising on just four deals worth a combined $940m (£458m). The firm's top 10 placing last year was largely driven by its involvement in the $9.8bn (£4.8bn) Saudi petrochemical project Rabigh, advising Sumitomo Chemical as joint sponsor.