Sajid Javid did not declare using offshore trust while he was working at the Treasury, it has been reported.
It comes after the former Chancellor was revealed to have enjoyed non-dom status before entering politics, and had an offshore trust - thought to have been located in a tax haven.
While the now-Health Secretary gave up his non-dom status in 2009, before entering politics, he retained the trust until 2012, by which time he was an aide to George Osborne.