Transport for London's (TfL) external legal spend grew by 15% last financial year after having fallen for four years, according to data obtained by Legal Week.

The figures, released under the Freedom of Information Act (FOI), showed TfL's total legal spend rose from £13m in the 2012-13 financial year to £14.9m in 2013-14.

Of the £14.9m total spend in the year to 31 March 2014, £11.3m, or 76%, was shared between 10 of the company's 11 panel law firms, all of which were appointed just before the four-year panel started in November 2012.

The remaining £3.6m, 24% of legal spending, was spent across 16 firms outside the panel.

Trowers & Hamlins was the only firm on the panel not to receive any fees in 2013-14.

In its response to the FOI request, TfL said: "TfL continuously seeks to ensure that it achieves value for money from its external lawyers including driving greater efficiencies through securing reduced fees. However, it is also necessary to use non-panel firms for other specialist work."

The main beneficiaries of the panel in 2013-14 were Herbert Smith Freehills (HSF), which received £4.2m in fees, followed by Eversheds, which secured £3.14m, and Ashurst, with just over £1m.

In the same year, Lewis Silkin received its first fees since winning a place on the panel in 2012, taking home £36,360 in fees.

The data also showed that before the uptick in spending in the last financial year total spending on external law firms fell 41% between 2009-10, when it stood at £22m, and 2012-13, when it reached £13m.

At the same time the authority's in-house legal team grew from 48 legal staff at the end of March 2010 to 83 at the end of March 2013.

The next year in-house legal staff numbers fell slightly as external legal spending rose by 15%.

But the figures showed that TfL's total legal staff costs have risen continuously over the last five years, increasing from £3.8m in 2009-10 to £8.5m in 2013-14.

The staff costs included legal support provided by TfL under shared services arrangements signed with the Greater London Authority, the Mayor of London's Office for Policing and Crime and the London Legacy Development Corporation in 2012.

TfL cut its core legal roster from 12 to 11 firms in 2012, with the appointments set to run through to 1 November 2016 when a new panel will be appointed.

In August 2014 HSF won an advisory role through the panel on a £660m update to TfL's Oyster payment card contract, which was led by Nick Pantlin, head of the firm's outsourcing and technology team.

Trowers & Hamlins declined to comment on its place on the framework.