Herbert Smith Freehills has joined the effort to try to stop Prime Minister Boris Johnson proroguing parliament.

Former PM Sir John Major is the latest high-profile figure to join the legal action attempting to prevent the U.K. Government from shutting down parliament. He has engaged HSF partner and London public law practice head Andrew Lidbetter to act for him.

Lidbetter has instructed The Rt Hon The Lord Garnier QC of 4 Pump Court Chambers and barrister Tom Cleaver of Blackstone Chambers to advise Sir Major.

Top-ranked administrative and public law and professional discipline partner Lidbetter has acted on several high-profile cases at HSF previously.

In 2015, he led the team that won a significant mandate from key firm client British American Tobacco, when the company challenged the U.K. Government's plain-packaging legislation.

Sir Major joins the legal action initiated earlier this week by Gina Miller, who instructed Mishcon De Reya to assist on her case against the government's prorogation. Mishcon has called on Lord Pannick QC, Warren Fitt and Tom Hickman to act in the case.

Mishcon made national headlines when it represented pro-EU campaigner and investment manager Miller in her successful case against the government regarding the triggering of Article 50. Last January, the Supreme Court ruled that the government could only trigger Article 50 after parliament had voted to begin the process of leaving the European Union.

Mishcon has a record of acting on political disputes. It briefly advised Brexit campaigning group Leave.EU on its appeal against its £70,000 fine from the Electoral Commission last year, but split from the client.