The Ministry of Justice has been criticised by the UK Statistics Authority over misleading figures used to justify legal aid cuts.

Sir Andrew Dilnot, chair of the independent body, wrote to legal aid minister Shailesh Vara highlighting concerns raised about the ‘nature, quality, timing and use’ of information provided by the ministry about the earnings of criminal barristers.

An ad hoc statistical release, ‘Barrister fee income from public sources 2012/13’ was published on 2 January, four days before planned industrial action by criminal lawyers in protest over the cuts.

Dilnot told Vara the ministry could have ‘increased compliance’ with the Code of Practice for Official Statistics, which requires publication in an ‘orderly manner, accompanied by commentary, analysis and information on quality and reliability’.

The authority found the information provided in the statistical report about barristers’ earnings was ‘potentially misleading’ as the notes explaining the figures were not presented alongside the data table.

It is critical of the MoJ’s use of ‘mean and median’ measures without advice on how to use the different measures.

‘Insufficient’ information, says Dilnot, is presented about the intended use of the statistics or about their strengths and limitations.

The authority said concerns had also been raised over statements made by ministers and officials over the average earnings of criminal barristers, following publication of the data.

The ministry stated that the ‘average’ earnings for a criminal barrister who works full time from legal aid is £84,000 a year.

The figure was not included in the statistical release and in fact represents the ‘mean’ fee from public funds for full-time barristers where any barrister with a fee income of less than £10,000 is excluded.

Shadow justice secretary Sadiq Khan MP described the MoJ as ‘an evidence-free zone’.

‘This latest slap-down is proof that even when ministers do use figures to support their arguments, they can’t be trusted,’ Khan said.

‘If the figures upon which the government is justifying their massive cuts and upheaval to legal aid are dodgy than it raises serious questions about the legitimacy of their plans.’

An MoJ spokesman said: ‘We stand by the figures that we have presented. We agree that this fee income is not the same as individual earnings, and this was stated in the statistical report we published on 2 January.’