The UK Government's Brexit department spent almost £1.2m on internal legal advice during the third quarter of its 2018-19 financial year, a new filing has revealed.

The Department for Exiting the European Union (DExEU) paid the Government Legal Department (GLD) a fixed fee of £1,191,250 for the period from October to December 2018. The department's financial year runs from 1 April to 30 March.

The disclosures come amid intense political wrangling over the government's legal position on the EU Withdrawal Agreement, a summary of which was published yesterday (3 December).

Senior MPs from six parties have written a joint letter to Commons Speaker John Bercow to ask him to launch proceedings of contempt against the government for failing to publish the "full and final legal advice on the Brexit deal" as ordered by parliament.

The GLD, a non-ministerial government department, operates outside of any political oversight. The £1.2m legal spend represents the largest sum paid by DExEU to an external organisation during the three-month period, ahead of the £720,000 paid to Boston Consulting Group.

The disclosures also reveal that DExEU paid nearly £40,000 to Interserve Facilities Management on estates and facilities costs during Q3, and more than £74,000 on "travel and subsistence" services from Clarity Travel Management.

The figures have been published as part of the DExEU's transparency data report, which details any spending in excess of £25,000.

A DExEU spokesperson said: "As we unpick more than 40 years of legal harmonisation with the European Union, it is essential to have the best legal advice.

"The government's internal legal services team has some of the finest lawyers in the country and of course we will make full use of them. But where appropriate, we will continue to draw on the advice and expertise of lawyers from the private sector."

Law firms providing legal support to the government during the Brexit negotiations have included Slaughter and May, which seconded City corporate partner Mark Horton to DExEU ahead of his retirement earlier this year.

Last year, DExEU spent £3.7m on legal costs during the last financial year, including more than £1.2m on Brexit-related litigation. Legal costs represented DExEU's second-most significant area of spending, behind staff costs of £14m for the year ending 31 March 2017.

Litigation costs represented almost a third of the department's total legal spend during the year, with the bulk of the £1.2m in litigation costs relating to the high-profile Article 50 legal challenge led by investment manager Gina Miller. The remainder of the litigation costs (£78,000) related to Article 127 litigation, which concerned Britain's membership of the European Economic Area.