The former Europe minister said he wanted to take "responsibility for my mistakes" after the Standards and Privileges Committee recommended he be suspended without pay and pension for a year - the longest suspension of an MP in living memory.
I have been overwhelmed by messages of support for my work as an MP on a range of issues but I accept that my parliamentary career is over.
I appreciate the committee's ruling that I made no personal gain and I regret my foolishness in the manner I chose to be reimbursed for work including working as the Prime Minister's personal envoy in Europe.
More top news
Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.
The former shadow work and pensions secretary is considered a more viable candidate than Angela Eagle, a Labour source has told ITV News.
As many as 10 people have been rescued following the raid, according to a Bangladeshi official.