A High Court judge has criticised the "extremely high" hourly rates charged by Weil Gotshal & Manges after the firm's client, BlackRock, claimed costs of almost £1.5m in a dispute with Middle Eastern energy company Dana Gas.

The dispute, which centred around the validity of $700m in Islamic bonds in which BlackRock was an investor, saw the asset management firm emerge as the successful party, with Dana ordered to pay its costs.

However, in a ruling on two costs applications made by BlackRock, Lord Justice Leggatt described the sum of £1.47m claimed by the asset manager as bearing "no reasonable relationship to the level of costs likely to be regarded as reasonable and proportionate".

Nine Weil fee earners worked on the case, charging hourly rates between £700 and £946. The judgment also states that a trainee working the case was charged out at £282 per hour.

Leggatt's judgment adds: "From my experience of assessing costs and reviewing cost statements and budgets in complex cases in the Commercial Court, competent representation can be obtained at much lower rates, in the region of around half the hourly rates paid in this case."

Of the 37 hours attending on counsel and 38 hours attending on BlackRock, more than half was spent by partners whose time was charged at £900 or £946 an hour, an amount of time described as "disproportionately large".

Leggatt ruled that the costs were "obviously unsustainable" and ordered Dana to pay a total of £425,000.

Weil instructed Andrew Scott of Blackstone Chambers as counsel, while Squire Patton Boggs acted for Dana Gas alongside Daniel Hubbard of One Essex Court.

Last year, RBS came under fire after its legal advisers at Herbert Smith Freehills (HSF) accumulated costs described as "staggering" by the judge overseeing the dispute over its controversial 2008 rights issue. The HSF team, led by partners Adam Johnson, Simon Clarke, Kirsten Massey and James Norris-Jones, accumulated about £100m in costs.

Weil was contacted for comment.