Kirkland & Ellis has acquired Washington DC litigation boutique Bancroft, a move which has seen the firm seal the trophy hire of former US solicitor general Paul Clement.

Clement (pictured), who left King & Spalding in 2011 to join Bancroft, is moving to Kirkland with the entire 17-lawyer firm, including founding partner Viet Dinh, a former assistant US attorney general for legal policy.

Bancroft, which is known for taking on politically conservative causes, will become part of Kirkland on 1 October.

"This is a natural combination of Kirkland as the number one global full-service firm and Bancroft as the leader in Supreme Court and appellate litigation – the fit is perfect," Dinh said in a statement. Clement added: "Kirkland has an unrivalled litigation practice and adding our appellate group will provide a remarkable team for our clients."

The recruitment of Dinh and Clement marks a major expansion of Kirkland's vaunted litigation department, which includes executive committee member Mark Filip, a former deputy US attorney general.

The news was met with surprise and admiration by the US Supreme Court Bar.

"It was a shock. Nobody was expecting this," said Lisa Blatt, head of Arnold & Porter's Supreme Court practice and a long-time friend of Clement. "This is the biggest shakeup in the Supreme Court Bar since Paul left King & Spalding in 2011."

Neal Katyal, a former acting US solicitor general, said the hire of Clement, Dinh and their team was a "huge coup for Kirkland".

Bancroft, which last year moved into new office space in Washington, DC, is known for hiring some of the nation's top appellate clerks to fill out its litigation ranks.

Bancroft's big litigation wins in recent years include representing Hobby Lobby in its challenge to the Affordable Care Act's contraception mandate, television networks fending off an online streaming service and members of US Congress in a fight over campaign finance.

During the past year alone, Bancroft advised the National Football League in defending the suspension of New England Patriots quarterback Tom Brady, the government of Argentina and the US Postal Service.

As for Kirkland, the addition of Bancroft is another prominent lateral hire by the Chicago-based firm, which took a hit earlier this year after a private equity group decamped for Sidley Austin in London. The abrupt loss of that group led Kirkland to extend its notice period for departing partners.