Theresa May intends to establish an offence of "illicit enrichment" for cases where a public official's assets have increased significantly without satisfactory explanation.
It is part of a wider shake-up of measures to tackle money laundering.
But Mrs May said it not a "knee-jerk" reaction to the Panama Papers.
She said the economy was "at risk of being undermined" by money laundering, illicit finance and the funding of terrorism.
'Significant threat'
Her new proposals - subject to a six-week consultation period being launched in the Commons later - plan to give the civil courts powers to impose new "unexplained wealth orders".
