Herbert Smith Freehills will next month extend its role advising an independent MP-led commission on the legal issues surrounding the Irish backstop – one of the central concerns of the Brexit process.

The firm secured a mandate earlier this summer to advise the 43-strong group of cross-party MPs 'alternative arrangements commission' on the Irish backstop impasse.

The alternative arrangements commission is co-chaired by culture secretary Nicky Morgan MP and former chief treasurer Greg Hands MP, and is made up of 43 cross-party MPs and Lords, including foreign secretary Dominic Raab MP and prominent Conservative backbencher Jacob Rees-Mogg MP.

In its first mandate for the commission, HSF last month drafted two protocols included in a wider interim report on alternative arrangements to the backstop, delivered to Prime Minister Boris Johnson. The firm said in a statement at the time: "The protocols capture in legal form a way forward which, if adopted, would avoid both a hard border and the Irish backstop ever being triggered."

HSF's team is led by Brexit director Paul Butcher, Brussels-based EU and trade consultant Eric White, EU and international trade partner Lode Van Den Hende, and trade consultant Dorothy Livingston.

Butcher told Legal Week: "The Prime Minister welcomed the interim report at the time it was published as 'brilliant'."

Earlier this week (August 20), the Prime Minister issued a letter to European Council president Donald Tusk, in which he called for the backstop to be replaced by "alternative arrangements".

Following the publication of the letter, HSF's Butcher added: "[The interim report] might be what [Johnson] had in mind in his letter to Donald Tusk on August 20, setting out his proposed way forward."