This follows the news that she will be leaving her position as managing director of mortgages at Vida at the end of March.
Jeremy Duncombe, current deputy chair, will step into the role effective immediately.
Sedgwick be joining Tandem Bank on 1 October after a period of gardening leave.
Since she accepted her new role, Tandem Bank has submitted an application to join IMLA.
Kate Davies, executive director of IMLA, said: “I am very grateful to Louisa for all the hard work she has done during her time as chair – some of which is not directly visible to all members, but which is nonetheless extremely important in representing members’ views to those who need to hear them.
“She has been pivotal in adding value to our membership throughout an extremely challenging 14-month period, and it’s disappointing that she’s unable to continue in this role for the remainder of her term.
“We wish her every success in her new role and look forward to welcoming her back into our ranks later this year.
“In the meantime, we’re delighted that Jeremy, who has long been a trusted member of IMLA’s management committee, is to take over as chair.”
Sedgwick added: “IMLA plays a fundamental role in supporting intermediary lenders by providing them with a unified voice, as well as a forum to discuss and debate key industry issues.
“I would have loved to have finished my full term as IMLA’s first female chair, however, I know the association is in safe hands with Jeremy.”
Duncombe said: “We’re all sad to see Louisa step down and we look forward to welcoming her back as soon as possible.
“She has made great strides in her time as chair, and I look forward to picking up where she left off, working hard to support IMLA’s membership over the coming months.”
